Controlling evaporative emissions in a fuel system

ABSTRACT

Methods and fuel systems to reduce evaporative emissions of a volatile fuel. A fuel tank contains fuel, a carburetor mixes air with the fuel from the fuel tank, and a plurality of fluid paths route fuel amongst and/or between the fuel tank and the carburetor. A valve actuation device stops flow of fuel in one or more of the plurality of fluid paths and the carburetor is adapted to be drained of fuel during engine shutdown to reduce or prevent evaporative emissions from the fuel system. The carburetor is preferably designed so as to minimize a volume of fuel contained therein.

FIELD OF THE INVENTION

This invention relates generally to volatile fuel storage and deliverysystems for internal combustion engines, and more particularly toevaporative emission controls adapted for use with a carburetor.

BACKGROUND OF THE INVENTION

A fuel storage and delivery system typically includes a fuel tank and acarburetor that are adapted for use in small, internal combustionengine-powered apparatuses. These apparatuses comprise a large consumermarket of popular lawn, garden, and marine products, which includehand-held equipment such as hedge trimmers, grass trimmers, andchainsaws and ground-supported equipment such as snow-blowers,generators, water pumps, power washers, sprayers, garden tractors,rototillers, and lawnmowers and marine equipment like inboard andoutboard motors and auxiliary generators. In recent years, such productshave been improved to reduce engine exhaust emissions, but now emphasisis being placed on improving these products to reduce non-exhaustemissions of volatile fuels and fuel vapors such as gasoline.

Volatile fuel emissions generally include hot soak losses, runninglosses, and diurnal losses. Hot soak and diurnal losses result fromemission of liquid or vaporous fuel and include permeation losses andevaporative losses. Permeation losses occur when fuel vapor permeatesthrough gaskets, fuel lines, or the fuel tank, and such losses are oftenabated by materials-oriented solutions such as integrating vapor barrierlayers within fuel lines and fuel tanks. Evaporative losses occur whenliquid fuel evaporates into hydrocarbon vapor and escapes into theatmosphere. Evaporation of liquid fuel into fuel vapor is usually due tovolatility of the fuel, vibration of the fuel tank and sloshing of thefuel therein, and temperature fluctuations of the fuel. Evaporativelosses most often occur 1) when fuel vapors in a fuel tank are vented tothe atmosphere, and 2) when fuel vapors in a carburetor are vented orotherwise escape to the atmosphere.

Fuel vapors are often vented from a fuel tank to the atmosphere to avoidbuild-up of positive pressure in the fuel tank. Hand-held equipmentoften uses diaphragm carburetors, which have spring-biased inlet valvesthat provide automatic shutoff against such positive tank pressures and,thus, do not require outward venting of the fuel tank. Butground-supported equipment typically uses float-bowl carburetors, whichbecome flooded under such positive tank pressures. When an engine with afloat-bowl carburetor is operating, fuel flows out of the fuel tank, andthe tank vent allows make-up air to enter the tank to replace the fueland thereby prevent a negative pressure condition therein. When theengine is not operating, however, fuel vapors may be permitted to ventout to the atmosphere from within the fuel tank to limit tank pressureand avoid carburetor flooding.

Fuel tank vapors are typically recovered using a fuel vapor recoverysystem. Such systems may include a carbon canister having activatedcharcoal therein that receives fuel vapors through a valve assemblymounted on the fuel tank and that communicates with an intake manifoldof the engine. During engine operation, negative pressure in the intakemanifold draws fuel vapor out of the carbon canister. The valve assemblyusually has a valve that is responsive to the level of liquid fuel inthe fuel tank that enables the valve to stay open at a sufficiently lowliquid level to permit fuel vapors to flow freely from the tank into thecarbon canister. When filling the tank, as the liquid fuel level risesto approach a desired maximum level of fuel, a float is raised to closethe valve to prevent liquid fuel from flowing through the valve and intothe vapor-receiving canister. While such a system works well, the addedcost of the carbon canister and float valve is prohibitive in manyapplications.

In addition to fuel tank vapor emissions, fuel vapors also tend toescape from a carburetor, particularly when the carburetor temperatureincreases due to heat soak back from a hot engine following engine shutdown and/or when the associated equipment is stored for an extendedperiod of time in an enclosure during warm weather. To illustrate, whena piece of engine-powered equipment is shut down after running at normaloperating temperatures, heat continues to transfer from a hot cylinderhead of the engine through an intake manifold to the carburetor.Moreover, the equipment may be placed in a storage enclosure withlimited or no ventilation, wherein the temperature may fluctuate over atwenty-four hour period from a daytime high exceeding 160 degreesFahrenheit to a nighttime low of 60 degrees Fahrenheit. Gasoline fuelevaporates over a wide temperature range with significant evaporationstarting at around 90 degrees Fahrenheit, with approximately thirtypercent by volume evaporating over a temperature increase to 160 degreesFahrenheit over a 24 hour period, and with about ninety plus percent byvolume evaporating over an increase to 350 degrees Fahrenheit over a 24hour period. In any case, the temperature of the liquid fuel within thecarburetor increases dramatically, thereby vaporizing some of the liquidfuel into fuel vapor.

Fuel escapes from some carburetors more readily than others. Hand-heldequipment typically includes two-stroke engines having diaphragmcarburetors, which tend to yield relatively low evaporative emissions.Unfortunately, however, diaphragm carburetors are not practical for allengine applications because they tend to have limited fuel meteringcapabilities, thereby leading to operational instability with certaintypes of engines. Precision fuel metering is generally not required inengines equipped with diaphragm carburetors, because such engines areusually operated in only two throttle settings—idle orwide-open-throttle (WOT)—such as in chainsaw or grass trimmerapplications. In contrast, ground-supported equipment typically haveengines with float-bowl carburetors that usually have relatively higherfuel metering capabilities to accommodate infinitely variable throttlesettings between idle and WOT, but tend to yield relatively higherevaporative emissions for several reasons.

First, the volume of fuel contained in a float bowl of a given floatbowl carburetor is usually several times greater than that contained ina metering chamber of a diaphragm carburetor. Commensurately, the totalvolume of liquid fuel that may be depleted from a float bowl carburetorwill be several times greater than that from a diaphragm carburetor.

Second, diaphragm carburetors are not continuously supplied with fuelfrom the fuel tank when the engine is not operating. In this case, fuelmay completely evaporate from within the diaphragm carburetor, but isnot continuously replenished with fuel from the fuel tank. This isbecause a typical diaphragm carburetor has an inlet needle valve that isstrongly biased closed to prevent entry of such fuel. The typical floatbowl carburetor, however, is continuously supplied with additionalliquid fuel from which additional evaporation takes place. This isbecause a typical float-bowl carburetor has an inlet needle valve thatis normally biased open unless the float bowl is filled with liquid fuelto a predetermined level, at which point a float gently raises the inletneedle valve to a closed position. As the liquid fuel vaporizes andescapes from the carburetor float bowl, the float and inlet needle valvedrop thereby allowing fresh liquid fuel to enter the float bowl throughthe float-actuated inlet needle valve under gravity draining from thefuel tank. Hence, hot soak and diurnal losses in a float bowl carburetorare also increased due to these vaporization-replenishment-vaporizationcycles.

Third, as indicated above, float-bowl carburetors are more sensitive tofuel inlet pressure than diaphragm carburetors. Consequently, the fueltank must have as low and constant an internal pressure as possible, yetstill support a high enough threshold pressure to minimize fuel vaporloss to the atmosphere. Unfortunately, conventional combination rubberduck bill and umbrella valves, typically associated with diaphragmcarburetor fuel systems, tend to suffer from hysteresis. Thus, suchvalves are not capable of repeatably holding a tank pressure closeenough to a predetermined threshold pressure.

In conclusion, equipment manufacturers are in need of a wide range ofreliable and comprehensive technological solutions to the problem of hotsoak and diurnal evaporative emissions of volatile fuel from a fuelsystem—particularly those solutions that address various escape routesof vapor emissions and that are robust and affordable to consumers.

SUMMARY OF THE INVENTION

According to exemplary embodiments, a method and a fuel system areprovided for controlling evaporative emissions of volatile fuel.According to the method, liquid fuel is supplied from a fuel tank into acarburetor during operation of an engine. Also, during shutdown of theengine, liquid fuel is stopped from flowing into the carburetor, andliquid fuel is drained out of the carburetor into a receptacle.According to the system, the fuel tank contains liquid fuel, and thecarburetor receives the liquid fuel from the fuel tank during operationof the engine and mixes air with the liquid fuel for supply to theengine. Moreover, during shutdown of the engine, a valve actuationdevice stops flow of fuel from the fuel tank to the carburetor and thecarburetor is drained of fuel to reduce or prevent evaporative emissionsfrom the fuel system.

According to preferred aspects of the method and system, the carburetormay be designed so as to minimize a volume of fuel contained therein,and may be drained of fuel by a manually actuated mechanical pump, anautomatically actuated mechanical pump, an electric pump, or gravitydraining. Likewise, the valve actuation device may be manually orautomatically actuated and may be mechanical or electrical.

According to another exemplary embodiment, a carburetor includes a body,a float that is carried by the body and that is movable about a pivotaxis. A fuel bowl is carried by the body for containing fuel andincludes a closed end that has an inside bottom surface sloped generallydownwardly away from the pivot axis. The closed end of the fuel bowlalso has a low-lying collection area and a fuel drain outlet disposedsubstantially at the low-lying collection area to enable substantiallycomplete drainage of fuel out of the fuel bowl.

According to a further exemplary embodiment, a fuel bowl is provided forcontaining fuel in a carburetor. The fuel bowl includes an open end, awall portion extending from the open end, and a closed end terminatingthe wall portion. The closed end includes a low-lying collection areaand a fuel drain outlet disposed substantially at the low-lyingcollection area to enable substantially complete drainage of fuel out ofthe fuel bowl.

According to an additional embodiment, a fuel pump is adapted to pumpfuel out of a fuel bowl of a carburetor. The fuel pump moves fuel fromthe fuel bowl into a fuel reservoir of the fuel pump during shutdown ofan engine, and moves fuel from the fuel reservoir to a fuel tank or backto the carburetor during startup of the engine. To this end, the fuelpump includes a diaphragm that divides an interior into the fuelreservoir on a reservoir side of the diaphragm and an oppositelydisposed actuation chamber on an actuation side of the diaphragm. Theactuation chamber accumulates pressurized air to displace the diaphragmagainst the force of a spring to purge the fuel reservoir. A fuel inletis in communication with the fuel reservoir, and an inlet check valve isin communication with the fuel inlet. Similarly, a fuel outlet is incommunication with the fuel reservoir, and an outlet check valve is incommunication with the fuel outlet.

According to a further embodiment, a fuel system supplies fuel to aninternal combustion engine, and includes a fuel tank for containing fueltherein, a carburetor in fluid communication with and elevated withrespect to the fuel tank and containing fuel therein, at least one valvein fluid communication between the fuel tank and the carburetor andbeing adapted to prevent flow of fuel into the carburetor at least whenthe internal combustion engine is not operating, and a pump in fluidcommunication with the carburetor and being adapted to pump fuel to thecarburetor substantially during startup and operation of the internalcombustion engine.

According to yet another embodiment, a method of reducing evaporativeemissions from a carburetor is provided wherein the carburetor includesa fuel bowl, a fuel inlet passage in communication with the fuel bowl,an inlet valve to valve the inlet fuel passage, a float pivotable abouta float pivot axis, and a fuel nozzle jet to communicate fuel within thefuel bowl to a fuel nozzle. The method comprises minimizing at least oneof the size of the inlet fuel passage or the lateral distance betweenfloat pivot axis and at least one of the vertical axis of the inlet fuelpassage or the inlet valve, and maximizing at least one of the fuelcontact surface area of the float or the lateral distance between thefloat pivot axis and a fuel buoyancy force associated with the float,wherein the volume of fuel within the fuel bowl is substantiallyminimized.

At least some of the objects, features and advantages that may beachieved by at least certain embodiments of the invention includeproviding a method, fuel system, carburetor, and pumps that enable areduction in the emission to the atmosphere of unburned fuel vapors,permit a carburetor fuel bowl to be drained during engine shutdown,improve control of fluid flow in a fuel system, can be actuated in avariety of ways including at least manual and powered or automatic, canopen and close various valves for controlled venting of a fuel tank andcontrolled supply of fuel to a carburetor, yield a compact constructionand arrangement, do not require active operator intervention to reduceevaporative emissions, are adaptable to a wide range of applications,are of relatively simple design and economical manufacture and assembly,rugged, durable, reliable and have a long, useful life in service.

Of course, other objects, features and advantages will be apparent inview of this disclosure to those skilled in the art. Other methods, fuelsystems, carburetors, and pumps embodying the invention may achieve moreor less than the noted objects, features or advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofthe preferred embodiments and best mode, appended claims, andaccompanying drawings in which:

FIG. 1 is a side view of a lawn mower that is equipped with a firstexemplary embodiment of a fuel system adapted for reduced evaporativeemissions;

FIG. 1A is a schematic view of a portion of an exemplary carburetor;

FIG. 2 is a pictorial schematic view of the exemplary fuel system ofFIG. 1 including an exemplary embodiment of a carburetor, a fuel shutoffvalve, and a first exemplary embodiment of a mechanical pump adapted foruse with an engine of the lawn mower of FIG. 1;

FIG. 3 is a cross-sectional view of the carburetor of FIG. 2;

FIG. 4 is an exploded perspective view of a fuel bowl and body of thecarburetor of FIG. 3;

FIG. 5 is a cross-sectional view of the mechanical pump of FIG. 2 in anengine off condition for storing fuel therein;

FIG. 6 is a cross-sectional view of the mechanical pump of FIG. 2 in anengine on condition wherein stored fuel has been purged therefrom;

FIG. 7 is a cross-sectional view of a check valve used in the mechanicalpump of FIG. 2;

FIG. 8 is a perspective view of a second exemplary embodiment of amechanical pump for use as an alternative with the fuel system of FIG.2;

FIG. 9 is a cross-sectional view of the mechanical pump of FIG. 8;

FIG. 10 is a partial exploded view of the mechanical pump of FIG. 8;

FIG. 11 is a cross-sectional view of a third exemplary embodiment of amechanical pump for use as an alternative with the fuel system of FIG.2;

FIG. 12 is a side elevational view of a fourth exemplary embodiment of amechanical pump for use as an alternative with the fuel system of FIG.2;

FIG. 13 is a top view of the pump of FIG. 12;

FIG. 14 is a cross-sectional view of the pump of FIG. 13, taken alongline 14-14 of FIG. 13;

FIG. 15 is a cross-sectional view of the pump of FIG. 13, taken alongline 15-15 of FIG. 13;

FIG. 16 is a partially exploded view of the pump of FIG. 12;

FIG. 17 is a top view of a valve plate shown in FIG. 16 of the pump ofFIG. 12;

FIG. 18 is a side view of the valve plate of the pump of FIG. 12;

FIG. 19 is a bottom view of the valve plate of the pump of FIG. 12;

FIG. 20 is a bottom view of a rotary valve shown in FIG. 16 of the pumpof FIG. 12;

FIG. 21 is an elevational view of the rotary valve of the pump of FIG.12;

FIG. 22 is a top view of the rotary valve of the pump of FIG. 12;

FIG. 23 is a top view of an exemplary embodiment of a combinedcarburetor and mechanical pump for use as an alternative with the fuelsystem of FIG. 2;

FIG. 24 is an end view of the combined carburetor and mechanical pump ofFIG. 23;

FIGS. 25 and 26 are partially exploded perspective views of the combinedcarburetor and mechanical pump of FIG. 23;

FIG. 27 is a block diagram schematic view of a second exemplaryembodiment of a fuel system that may incorporate one or more of thepreviously disclosed embodiments and that is depicted in an engine onmode;

FIG. 28 illustrates the fuel system of FIG. 27 depicted in an engineshutdown mode;

FIG. 29 illustrates the fuel system of FIG. 27 depicted in an engine offmode;

FIG. 30 illustrates the fuel system of FIG. 27 depicted in an enginestartup mode;

FIG. 31 is a pictorial schematic view of a third exemplary fuel systemof FIG. 1 including an exemplary embodiment of a carburetor, a four-wayfuel fitting, and a pneumatic fuel pump adapted for use with an engineof the lawn mower of FIG. 1;

FIG. 32 is a cross-sectional view of the pneumatic fuel pump of thesystem of FIG. 31;

FIG. 33 is a cross-sectional view of the carburetor of the system ofFIG. 31;

FIG. 34 is a cross-sectional view of the four-way fuel fitting of thesystem of FIG. 31;

FIG. 35 is a block diagram schematic view of a fourth exemplaryembodiment of an electrically-actuated fuel system; and

FIG. 36 is a pictorial schematic view of several components of theelectrically-actuated fuel system of FIG. 35.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overview

In general, and before referring to the drawing figures, a method, asystem, and various apparatuses are disclosed herein. The variousexemplary embodiments are all adapted for controlling evaporativeemissions of volatile fuel from escaping a fuel system for an engine ofa lawn and garden product, or any number of recreational, marine,industrial, and/or agricultural products. The embodiments are adaptedfor use with gravity draining or fuel pump fuel systems for two or fourstroke engines, which may be manual start or electric start engines. Theexemplary embodiments are structurally different, but include a numberof features in common that will be discussed first herein below.

According to the preferred embodiments disclosed herein, a fuel systemis provided for containing, routing, and metering fuel, and deliveringthe metered fuel to a fuel intake of an internal combustion engine, andthe fuel system generally includes a fuel tank and a carburetor. Thefuel tank receives a quantity of volatile liquid fuel and is providedfor containing the fuel therein until the fuel is delivered to thecarburetor. In turn, the carburetor receives the fuel from the fuel tankand is particularly adapted for mixing air with the fuel to create anoptimal air/fuel mixture for use by an internal combustion engine. Thefuel system preferably further includes a valve and/or valve actuationdevice in fluid communication with the fuel tank and carburetor forpermitting flow of fuel through certain fluid paths of the fuel systemwhen the engine is operating, and for preventing flow of fuel throughcertain fluid paths when the engine is not operating. The fuel systemalso preferably includes a mechanical accumulator or pump that withdrawsfuel from the carburetor substantially during engine shut down andsupplies or returns fuel to the carburetor substantially during enginestartup. Alternatively, the fuel system may include the carburetorelevated with respect to the fuel tank to enable gravity draining offuel from the carburetor.

In any case, liquid fuel is stopped from flowing to the carburetor, isdrained and/or withdrawn from the carburetor, and is stored in apreferably sealed receptacle such as the fuel tank and/or a fuelreservoir separate from the tank, substantially during engine shut down.Substantially during engine startup, fuel is permitted to flow to thecarburetor and the fuel previously drained and/or withdrawn from thecarburetor is returned to the carburetor or to the fuel tank from thereceptacle.

The fuel system thereby reduces evaporative emissions from a carburetorand eliminates the need to manually drain fuel from a carburetor priorto transport of the engine-operated apparatus because the carburetor isautomatically drained at each engine shut down. Accordingly, the fuelsystem will be particularly useful on certain engine-powered apparatussuch as marine outboard motors because it is common to tilt suchoutboard motors up and out of the water when not being used and, thus,liquid fuel can leak therefrom. With the present fuel system, however,fuel is prevented from spilling out of the carburetor and into the wateror into a boat to which the outboard motor is attached. The present fuelsystem is also particularly useful with landscaping apparatus such aswalk behind lawmnowers because such equipment is typically tilted on itsside for maintenance. Using the present fuel system, fuel will no longerspill from the tilted equipment. Therefore, the present fuel systemreduces or prevents fuel spills and, thus, fuel emissions from equipmentthat may be tilted for one reason or another.

The exemplary methods and systems include conventional elements in theart but also may include particularly preferred aspects. In a firstpreferred example, the fuel tank is of substantially conventionalconstruction, having sidewalls, a bottom wall terminating the sidewalls,a fuel filter disposed in a depressed portion of the bottom wall, and anoppositely disposed top wall terminating the sidewalls and including afuel cap mounted thereto. Preferably, however, the fuel tank includes apressure relief valve integrated into a fuel cap or vapor vent outletfitting that may be mounted to the top of the fuel tank. In a secondpreferred example, the carburetor is preferably of substantiallyconventional construction except for a presently preferred fuel bowldesign. The carburetor includes a body having a mixing passage formixing air and fuel therein, a choke valve rotatably disposed in themixing passage, a throttle valve rotatably disposed in the mixingpassage downstream of the choke valve, the preferred fuel bowl carriedby the body for receiving liquid fuel from the fuel tank and containingthe fuel in a fuel chamber defined therebetween, and a fuel nozzle influid communication between the mixing passage and the fuel bowl. Thepreferred fuel bowl includes an open end, a wall portion extending fromthe open end, and a closed end that terminates the wall portion and thatincludes a low-lying collection area and a fuel drain outlet to enablesubstantially complete drainage of fuel out of the fuel bowl.

Exemplary Embodiments

Referring now in detail to the drawing figures, an exemplary embodimentof a fuel system is shown in FIGS. 1 and 2. Next, an exemplaryembodiment of a preferred carburetor is depicted in FIGS. 2 through 4.Subsequently, an exemplary embodiment of a mechanical pump isillustrated in FIGS. 5 through 7. Then, a second exemplary embodiment ofa mechanical pump is portrayed in FIGS. 8 through 10. A third exemplaryembodiment of a mechanical pump is shown in FIG. 11. A fourth exemplaryembodiment of a mechanical pump is represented in FIGS. 12 through 22.An exemplary embodiment of a combined carburetor and mechanical pump isdepicted in FIGS. 23 through 26. An exemplary embodiment of a genericfuel system is illustrated in block diagrams of FIGS. 27 through 30. Anexemplary embodiment of a gravity draining fuel system and componentsare illustrated in FIGS. 31 through 34. Finally, an exemplary embodimentof an electrically-actuated fuel system and components are illustratedin FIGS. 35 and 36.

Exemplary Embodiment of a Fuel System

FIG. 1 illustrates evaporative emission control apparatus 10 that isadapted for any type of useful apparatus such as a push or walk-behindlawn mower 12 having a combustion engine 14. A fuel tank 16 containsfuel, which flows to a carburetor 18 during engine startup and/or whenthe engine 14 is running, but is stopped from flowing during engineshutdown and/or when the engine 14 is not running. The fuel tank 16,carburetor 18, and fuel passages therebetween at least partially definea fuel system.

As used herein, the term “fuel” encompasses liquid fuel, fuel vapor, andany liquid-vapor phase combination thereof. Also, the term “shutdown” issynonymous with cut-off, shut off, deactivated, turned off, killed, todisable, switched off, inoperative, and the like. Those of ordinaryskill in the art will recognize that shutdown means the cessation ofengine operation such that a crankshaft of the engine slows down andeventually stops due to a lack of fuel and/or ignition supply to theengine. Moreover, the phrase “startup” is synonymous with activated,turned on, to enable, switched on, operative, and the like. Those ofordinary skill in the art will recognize that startup means thebeginning of engine operation such that a crankshaft of the engine isset in motion and fuel and spark are supplied to a combustion chamber ofthe engine. Also, the term “operating” is synonymous with running andbasically means that the engine is doing work from input of fuel andignition of that fuel.

Preferably, manual means are provided for opening one or more fuelpassages of the fuel system to permit fuel flow—such as a mechanical,multi-action valve, or valve actuation device 20, of the emissioncontrol apparatus 10. The valve actuation device 20 may be actuated topermit flow of fuel when the engine 14 is operating. The valve actuationdevice 20 may be a stand alone sub-assembly or may be carried by thecarburetor 18, and may be manually actuated to an engine-on or valveopen position.

As defined herein, the term “valve” means any flow-control apparatus, orone or more features of an apparatus, that is used in regulating flow offluids in one or more passages. As also defined herein, “valve actuationdevice” encompasses a device that may include valves, or valve featuresor elements, integrated therein or in a component thereof, or that mayinclude valve actuating members or portions, which actuate a separatevalve that is not integral to the device itself. In other words, thepresent invention contemplates that the different valve constructionsand arrangements, and the fluid conduits of the various embodiments maybe substituted for one another or combined in any desired manner.

In contrast with the manual means, automatic means are preferablyprovided for stopping one or more fuel passages of the fuel system tostop fuel flow. In other words, the valve actuation device 20 ispreferably automatically actuated to an engine-off or valve closedposition to stop flow of fuel. The valve actuation device 20 mayinclude, or actuate, only one valve, but preferably includes and/oractuates at least two valves substantially simultaneously or with somepredetermined delay therebetween, if desired.

Still referring to FIG. 1, the valve actuation device 20 is actuated bya lever 22 that is preferably controlled via a push-pull cable 24, suchas a Bowden cable, which is connected to a safety lever or bail 26 thatis pivotably attached to a handle 28 of the lawn mower 12. The push-pullcable 24 may be spliced, or may include a plurality of individualcables, in order to additionally engage a pivoting engine ignitionshut-off arm or switch 30 and/or other valves or devices. In otherwords, the emission control apparatus 10 may be actuated substantiallysimultaneously with an engine ignition control apparatus of the lawnmower 12, wherein a user may release the spring-biased safety lever 26to also open an ignition circuit to shut off electrical power to a sparkplug of the engine 14. Likewise, the emission control apparatus 10 mayalso be actuated substantially simultaneously with a blade brake, whichapparatus is well known to those of ordinary skill in the art. Thesafety lever 26 thereby pivots from a run or advanced position as shownin phantom lines at 26′ to its biased shut-off position as shown insolid lines at 26. The safety lever 26 is preferably spring-loaded, orspring-biased, so that the user must actively and continuously hold thesafety lever 26 in the run position 26′ when operating the lawnmower, orthe engine 14 will cease to operate.

Referring now to FIG. 2, the fuel system includes the fuel tank 16, thecarburetor 18, the valve actuation device 20 in fluid communicationtherebetween, and a mechanically actuated accumulator or pump, ormechanical pump 32, in fluid communication between the carburetor 18 andthe fuel tank 16. When the engine is operating, liquid fuel 34 flowsfrom the fuel tank 16 through a fuel filter 36, fuel lines or fluidpaths 38, 38′, 38″, and the valve actuation device 20, into thecarburetor 18. In general, however, the valve actuation device 20 is ina normally closed position to stop flow of liquid fuel through the fuellines 38′, 38″ from the tank 16 to the carburetor 18. The valveactuation device 20 is adapted to permit flow of liquid fuel into thecarburetor 18 when the internal combustion engine is operable, such aswhen a user holds the safety lever 26 in the run position 26′. The valveactuation device 20 is adapted to prevent flow of liquid fuel into thecarburetor 18 during engine shutdown and when the engine is notoperating, thereby reducing escape of evaporative emissions of volatilefuel from the fuel system.

As defined herein the terminology “fluid path” or “fuel path” means anyroute, conduit, or the like for communicating or conveying fluidtherethrough. The term “conduit” is likewise broadly defined herein toinclude integral passages cast, machined, or otherwise formed in thecarburetor or individual fuel lines, hoses, or the like, for conveyingfluid either liquid or vaporous. In other words, the fuel conduitsdescribed herein may take various forms and may be consideredsub-components or sub-features of the carburetor or fuel tank or may beconsidered individual components.

The pump 32 is in fluid communication with the carburetor 18 via fuellines 40, 40′ and, as will be described in detail below, is adapted towithdraw or pump fuel out of the carburetor 18 and into a receptacle,substantially during engine shutdown, for example, as a result of a userreleasing the safety lever 26 from its engine on position 26′ to itsbiased off position 26. Preferably, the receptacle is sealed and is areservoir defined within the pump 32 itself, but the receptacle may beseparate from the pump and may also be the fuel tank 16 itself or someother separate receptacle. As also will be described in detail below,the pump 32 is adapted to pump fuel out of its reservoir and to anotherreceptacle such as the fuel tank 16 or back to the carburetor 18substantially during engine startup, for example, as a result of a usergripping the safety lever 26 to its engine on position 26 andmechanically or electrically activating the ignition of the engine.

Those of ordinary skill in the art will recognize that the phrase“substantially during” encompasses a time period not only during thereferred to event, but also suitable periods before and after the event.For example, the pump 32 may begin to pump fuel out of the carburetor 18for a few seconds before the engine starts to shut down and may continueto pump fuel for a few seconds after the engine has shut down. Inanother example, the pump 32 may begin to pump fuel out of the reservoirfor a few seconds before ignition of the engine and may continue to pumpfuel for a few seconds after the engine has been started and is running.

The tank 16 is provided for containing liquid and vapor fuel and may besealed with a cap or closure 42, wherein the tank 16 and closure 42 maybe composed of any suitable materials including a multi-layer plasticcomposition having a vapor barrier layer. As one example withoutlimitation, the tank 16 and closure 42 may be composed of anethylene-vinyl-alcohol barrier layer that is sandwiched between highdensity polyethylene structural layers. Similarly, the fuel lines 38, 40may be composed of multiple layers and by way of example, may be threelayer non-conductive fuel lines such as Permblok® 330 hoses commerciallyavailable from TI Automotive of Warren, Mich. The closure 42 may be aventless closure, or a vented closure as shown such as that disclosed inU.S. patent application Ser. No. 10/955,133, filed on Sep. 30, 2004, andentitled EVAPORATIVE EMISSIONS CONTROLS IN A FUEL SYSTEM, which isassigned to the assignee hereof and is hereby incorporated herein byreference. The fuel filter 36 is optional and is provided for filteringliquid fuel exiting the fuel tank 16, and may be any one of a multitudeof conventional fuel pick-up filters, which are well known in the art.

The fuel system preferably incorporates the mechanical shutoff valve 20that is in communication with the fuel lines 38 and may be similar tothat which is described in U.S. patent application Ser. No. 10/955,795,filed Sep. 30, 2004 and entitled EVAPORATIVE EMISSIONS CONTROLS, whichis assigned to the assignee hereof and is hereby incorporated herein byreference. The shutoff valve includes the lever 22, which is controlledvia the push-pull cable to normally stop flow of fuel through the fuellines 38 from the tank 16 to the carburetor 18, unless the shutoff valveis deactivated or opened by a user moving the safety lever 26 to the runposition 26′.

Exemplary Embodiment of a Carburetor

Still referring to FIG. 2, and aside from the novel features describedherein, the carburetor 18 may otherwise be constructed consistent with alow evaporative emission float-bowl carburetor, such as thoseexemplified by U.S. Pat. No. 6,561,495 or U.S. Pat. No. 6,640,770, bothof which are assigned to the assignee hereof and incorporated herein byreference in their entireties for exemplary purposes. For example, thecarburetor 18 includes a carburetor body 44 with a passage 45 for mixingair with fuel for delivery to an intake of an engine. The body 44includes a choke lever 46 for operating a choke valve 47, a throttlelever 48 for operating a throttle valve 49, and a fuel inlet fitting 50that connects to one of the liquid fuel lines 38″. The carburetor 18also includes a preferred float bowl or fuel bowl 52 carried by the body44. The fuel bowl 52 may be of preferred design and construction asdescribed below after the following background discussion.

FIG. 1A illustrates a cross section of a portion of an exemplarycarburetor 151 including a float valve arrangement. The carburetor 151includes a float bowl 152 mounted to a body 153 to define a fuelchamber. The carburetor 151 includes a fuel and air mixing passage 155extending therethrough and a fuel nozzle 157 in communication with themixing passage 155 to deliver fuel 159 from the fuel chamber or bowl 152to the mixing passage 155. A fuel inlet passage 161 extends through aportion of the body 153 and terminates in a valve seat 163. An inletneedle valve or float valve 165 is adapted to valve the fuel inletpassage 161 by sealing against the valve seat 163 when a float arm 167is raised by buoyancy of a float 169 in the liquid fuel in the fuelchamber and by separating from the valve seat 163 when the float arm 167lowers. A restricted orifice or fuel nozzle jet 171 is provided througha fuel nozzle post 173 to meter flow of the liquid fuel 159 from thefuel chamber into a fuel well defined at least partially by the nozzle157. The float valve 165 seats and unseats to block and permit flow offuel through the inlet passage 161 into the fuel chamber in response tothe changing fuel level via movement of the float arm 167 about a pivotaxis Z.

Typically, the quantity of liquid fuel in a fuel bowl 152 is muchgreater than is needed for proper engine operation. Thus, one way toreduce evaporative emissions from a carburetor fuel bowl is to reducethe quantity of liquid fuel in the bowl to substantially the minimumquantity of liquid fuel needed for proper engine operation under alloperating conditions likely to be encountered by the engine application.According to the following analysis, fuel volume in the carburetor 151may be minimized.

In addition to a weight W_(v) of the float valve 165, an incoming fuelpressure P acts on an exposed area A_(i) of the float valve 165 thatcorresponds to an exposed diameter D_(i) of the float valve 165, tounseat the float valve 165 from the valve seat 163. In contrast, thefloat valve 165 tends to be seated against the valve seat 163 by abuoyancy force F_(f) of the float 169 minus the weight W_(f) of thefloat 169. The buoyancy force F_(f) is the volume V_(f) of fueldisplaced by the float 169 multiplied by the density of the fuel 159.The volume V_(f) of fuel displaced is the horizontal surface area A_(f)of the float 169 that is exposed to the fuel 159 multiplied by avertical distance h₂ between the bottom of the float 169 and the surfaceof the fuel 159. It is desirable to maintain a vertical distance h₁between the jet 171 and the surface of the fuel 159 as constant aspossible.

A lateral distance ‘a’ is depicted between the float pivot axis Z and anoperating or vertical axis of the float valve 165 and inlet passage 161.A lateral distance ‘c’ is shown between the float pivot axis Z and thelateral centerline of the weight distribution of the float 169 and floatarm 167. The weight of the float 169 and float arm 167 is represented byW_(l), and those of ordinary skill in the art will recognize that thefloat 169 and the float arm 167 may be integrated into one component orfloat. Moreover, a lateral distance ‘b’ is illustrated between the floatpivot axis Z and the vertical axis of the fuel buoyancy force Ff.

Summing torques about the float pivot axis Z yields the followingequation: a(PA_(i)+W_(v))+cW_(l)=bF_(f). It may be assumed that W_(v)and W_(l) are negligible relative to the other forces involved. Assumingthe density of the fuel is 0.73 specific gravity, the float buoyancyforce F_(f) may be substituted for 0.73V_(f). The exposed float valvearea A_(i) may be expressed as πD_(i) ²/4. These expressions may besubstituted to yield the following modified equation: a(0.785 PD_(i)²)=b(0.73 V_(f)). Solving for V_(f) yields the following equation:V_(f)=1.076a(PD_(i) ²)/b. Substituting (A_(f)×h₂) for V_(f) yieldsA_(f)×h_(2=1.076)a(PDi²)/b. Therefore, h₂=1.076aPD_(i) ²/(bA_(f)).

From the above, it can be seen that h₂ is proportional to P for anygiven design, assuming A_(f) is constant. In other words, if P doubles,then h₂ doubles. To keep the absolute change of h₂, and of h₁, to aminimum, h₂ should be as small as possible so that multiples of h₂ arealso relatively minimal. Therefore, a and D_(i) should be as small aspractical and A_(f) and b should be as large as practical.

Therefore, a method of reducing evaporative emissions from a carburetorincludes minimizing one or the other or preferably both of the size ofthe inlet fuel passage 161 or the lateral distance ‘a’ between the floatpivot axis Z and at least one of the vertical axis of the inlet fuelpassage 161 or the inlet valve 165, while simultaneously maximizing oneor the other or preferably both of the fuel contact surface area A_(f)of the float 169 or the lateral distance ‘b’ between the float pivotaxis Z and the vertical axis of the fuel buoyancy force, wherein thevolume of fuel within the fuel bowl is substantially minimized. Forexample, the volume of fuel may be minimized from a typical value ofabout 25 to 35 cc for a small engine carburetor to a value of about 12to 16 cc. In other words, the volume of fuel may be reduced by as muchas 50% or more. The term minimizing includes substantially minimizingand does not require absolutely minimizing, nor does it require areduction of 50% or more. The term maximizing includes substantiallymaximizing and does not require absolutely maximizing something.

Moreover, the fuel volume on the side of the nozzle 157 opposite thefloat 169 (i.e. in FIG. 1A the pivot axis side of the nozzle 157) doesnot contribute to the buoyancy of the float 169. Therefore, it ispreferred to keep that fuel volume to a minimum. This may beaccomplished by modifying the fuel bowl 152 to yield a minimum volume offuel on the pivot axis side of the nozzle 157 in favor of relativelymore fuel volume on the float side of the nozzle 157. In other words,the fuel bowl 152 may be modified to include an angled inside bottomsurface that slopes downwardly and laterally away from the pivot axis Zof the float arm 167.

Such a fuel bowl modification is depicted in FIGS. 2 through 4, whichshow the preferred carburetor 18 with the angled fuel bowl 52. As bestshown in FIGS. 3 and 4, the fuel bowl 52 includes an open end 54, a wall56 extending downward from the open end 54, and a closed end 58terminating the wall 56. The closed end 58 includes an inside bottomsurface 60, 60′ that is sloped at the same or a similar angle withrespect to the angle of a float arm 62 when the float arm 62 is in thefull open position. The fuel chamber of the carburetor 18 is basicallydefined between the inside bottom surface 60, 60′ of the fuel bowl 52and the body 44. To accommodate as large a distance as possible betweena float pivot axis Z′ and a lateral centerline of a float 64, it isdesirable to keep the left side of the float 64 as close as practicableto the inside surfaces of the wall 56 of the float bowl 52, such asabout 0.050″, taking manufacturing tolerances into consideration. Whilethis bowl design minimizes fuel volume to reduce evaporative emissions,it is also desirable to further enable substantially complete drainageof liquid fuel from the fuel bowl 52 of the carburetor 18. As usedherein, the phrase “substantially complete” encompasses more than 50%drainage and preferably encompasses greater than 75% drainage.

Accordingly, the fuel bowl 52 is provided with a low-lying collectionarea 66 and a fuel drain outlet 68 disposed substantially at thelow-lying collection area 66. In other words, the fuel drain outlet 68is positioned in such proximity to the low-lying collection area 66 soas to enable substantially complete drainage of liquid fuel out of thefuel bowl 52 through the fuel drain outlet 68. As used herein, thephrase “low-lying collection area” means a portion of the fuel bowl thatis relatively low compared to the rest of the fuel bowl (when in itsnormal attitude or orientation when in use in a given engineapplication) to enable fuel to accumulate there under the force ofgravity. As best shown in FIG. 4, the low-lying collection area 66 is influid communication with the fuel chamber via a gutter or channel 70provided in the closed end 58 of the fuel bowl 52. The channel 70 slopesaway from the inside bottom surface 60′ toward the low-lying collectionarea 66 to enable liquid fuel to exit the fuel bowl 52 through a fitting72 extending through the drain outlet 68.

Accordingly, the method of reducing evaporative emissions from thecarburetor is further enhanced by angling an inside bottom surface of afuel bowl, preferably in a direction laterally and downwardly away fromthe float pivot axis, and more preferably, toward a low-lying collectionarea of the fuel bowl. But, to more fully ensure substantially completedrainage of liquid fuel from a carburetor, it is further desirable toprovide means for removing the liquid fuel from a fuel bowl of thecarburetor.

First Exemplary Embodiment of a Mechanical Pump

The fuel is removed from the carburetor fuel chamber or bowl 52preferably using a fuel transfer and storage unit, such as themechanical accumulator or pump 32 of FIG. 2. It is contemplated that anysuitable type of pump could be used including an electrically-actuatedpump (“electric pump”), pneumatic mechanical pumps, plunger stylemechanical pumps, and the like. As also shown in FIGS. 5 and 6, the pump32 includes a housing 74 and a cover 76 attached to the housing 74, suchas by a circumferential crimp joint as shown, to define an interior 78.The housing 74 and cover 76 are preferably stamped or machined frommetal, molded from a polymeric material, or the like.

A diaphragm 80 is disposed within the interior 78 and is sealinglyengaged between the cover 76 and housing 74 by the crimp joint to dividethe interior 78 into a fuel reservoir 82 on a reservoir side of thediaphragm 80 for carburetor bowl drainage, and an actuation chamber 84on an actuation side of the diaphragm 80 used primarily for advancingthe diaphragm 80. As used herein, the term “reservoir” encompasses anysuitable receptacle for storing fuel drawn from the carburetor bowl 52to be recycled thereto or to the fuel tank. The diaphragm 80 may becomposed of any suitable fuel resistant elastomeric material, or othermaterial suitable for use in a fuel system.

The phrase “polymeric material” generally includes relativelyhigh-molecular-weight materials of either synthetic or natural originand may include thermosets and thermoplastics. For use in fuel systems,the polymeric material preferably exhibits suitable non-permeation andresistance to hydrocarbon fuels such as gasoline, gasohol, alcohol, anddiesel. The term elastomeric also encompasses any of various elasticsubstances resembling rubber, such as a fluorocarbon like Viton®, anitrile such as acrylonitrile-butadiene, or the like. In general, thematerials used for the components may be selected based on theirdimensional stability, non-permeation, and resistance to swelling anddegradation in warm and cold flexible hydrocarbon fuel environments.

A coiled metal compression spring 86 is disposed within the fuelreservoir 82 to yieldably bias the diaphragm 80 against an insidesurface of the cover 76. A protective cup or plate 88 is disposedbetween the diaphragm 80 and the adjacent end of the spring 86. Theother end of the spring 86 circumscribes a central boss 90 that includesfuel inlet and outlet check valves 92, 94 disposed in fluidcommunication with the fuel reservoir 82 and inlets and outlets 96, 98of the pump 32. The inlets and outlets 96, 98 include respective inletand outlet fittings 100, 102 inserted therein. At an opposite end of thepump 32, the cover 76 includes an integral fitting 104 defining apressure pulse port 105 with a pneumatic check valve 106 disposedtherein in communication with the actuation chamber 84.

The pneumatic check valve 106 is best depicted in FIG. 7 and includes agenerally annular housing 108 defining a through passage 110 includingfirst and second counterbores 110′, 110″. The check valve 106 ispreferably composed of metal, polymeric, and/or elastomeric components.An inlet end includes an annular valve seat 112 for engaging a disc 114in its closed position seated against the valve seat 112. At an outletend of the check valve 106, an open valve retainer 116 is inserted intothe second counterbore 110″ and includes projections 118 for supportingthe disc 114 in its open position bearing on the projections 118. Thehousing 108 is crimped over to retain the valve retainer 116. As shown,the check valve 106 is closed such that fluid cannot easily passtherethrough from the outlet end to the inlet end, unless the fluid isunder such pressure as to flow through a pinhole 120 in the disc 114.When the check valve 106 is open, the disc 114 unseats and locatesagainst the projections 118 of the retainer 116 such that fluid entersthe through passage 110 at the inlet end and easily flows around thecircumferential periphery of the disc 114, through the open retainer116, and out the outlet end of the valve 106. The fuel check valves 92,94 are substantially similar in construction and operation, except thatthere are no pinholes provided in discs thereof.

During engine operation, the pump 32 is powered by positive pressurepulses to move the diaphragm 80 from its retracted position shown inFIG. 5 to its advanced position shown in FIG. 6. In its retractedposition of FIG. 5, liquid fuel that was previously received from thecarburetor bowl 52 is temporarily stored in the fuel reservoir 82. Manyengines, when operating, generate a positive pressure pulse in theircrankcase that may be used to power the pump 32. In one example shown inFIG. 2, an engine crankcase C is in fluidic communication with the port105 of the pump 32. Accordingly, when the engine is operating, positivepressure pulses of air pass through the check valve 106 and into theactuation chamber 84 of the pump 32. As more and more air enters theactuation chamber 84 through the check valve 106, air pressure increasesin the actuation chamber 84 and thereby displaces the diaphragm 80 in anadvancing direction against the force of the spring 86. As shown in FIG.6, the liquid fuel has substantially been forced out of the fuelreservoir 82 through the outlet check valve 94 and outlet 98 bydisplacement of the diaphragm 80 from its retracted position against theinside surface of the cover 76 to its fully advanced position againstthe boss 90 of the housing 74. Referring to FIG. 2, the fuel is forcedout of the pump 32 through the fuel line 40′ and back toward the fueltank through lines 40′ and 38 and/or toward the carburetor 18 throughthe fuel lines 38′, 38″ as the shutoff valve 20 is open during engineoperation. Although some fluid from the actuation chamber 84 may passthrough the pinhole 120 of the check valve disc 114 during engineoperation (when a negative pressure pulse is produced in the enginecrankcase), the pinhole 120 is preferably sized so that the magnitudeand frequency of the positive pressure pulses are sufficient to maintainthe diaphragm 80 in its advanced state against the housing 74 despiteany pressure lost through the pinhole 120.

The diaphragm 80 maintains its advanced position until the engine stopsand, therefore, the pressure pulses from the crankcase cease. When theengine stops, the pressure in the actuation chamber 84 is relieved orvented through the pinhole 120. The force of the spring 86 is thus ableto move the diaphragm 80 toward the cover 76 thereby increasing thevolume of the fuel reservoir 82 and simultaneously decreasing the volumeof the actuation chamber 84 wherein fluid is slowly vented through thepinhole 120 in the check valve disc 114. Referring to FIGS. 3 and 5, asthe volume of the fuel reservoir 82 increases, liquid fuel is drawn outof the carburetor bowl 52 through the drain outlet 68, fitting 72, andthe fuel line 40 and into the fuel reservoir 82 through the inlet 96 andinlet check valve 92. The maximum volume of the fuel reservoir 82 of thepump 32 is preferably greater than or at least equal to the volume offuel held in the fuel bowl 52 of the carburetor 18 during normal engineoperation.

Referring also to FIG. 2, substantially during engine shutdown, the fuelshutoff valve 20 closes to stop fuel flow to the carburetor 18.Accordingly, little to no fuel is left in the fuel bowl 52 of thecarburetor 18, thereby greatly reducing evaporation and escape of fuelvapor from the carburetor 18 into the atmosphere. The liquid fuel issealed within the fuel tank 16, fuel lines 38, 38′, 38″, 40′, and thepump 32. Fuel in the fuel reservoir 82 of the pump 32 may tend topermeate through the diaphragm 80. Therefore, the spring plate 88 isprovided to create an annular seal between the plate 88 and the cover76. Fuel cannot pass through the plate 88 to reach the actuation chamber84 and any fuel permeating the sides of the diaphragm 80 is trapped bythe cover 76. When the engine is restarted, such permeated fuel vaporswill preferably be returned to the engine crankcase and, vented to theengine air intake.

Some engine-powered apparatuses may not be amenable to use with thepreviously described pneumatic pump 32. For example, some engines maynot generate crankcase pressure pulses of sufficient magnitude to powera pneumatic pump that withdraws fuel from a carburetor and returns it toa fuel tank. Crankcase pressure pulses of a relatively small four strokeengine are typically about 1.0 to 1.5 in Hg, which is equivalent toabout 18 to 27 inches of fuel head. Accordingly, if the level of fuel ina fuel tank is greater than 18 to 27 inches above the associatedpneumatic pump, then the pneumatic pump will not be able to move liquidfuel back to the tank under power from the crankcase pressure pulses.Moreover, pressure build up within a fuel tank may make it difficult ifnot impossible to move liquid fuel from the pump to the fuel tank. Theforce of the spring should be of sufficient magnitude to overcome theinternal resistance of the diaphragm and to draw fuel from the fuelbowl. Yet, the net pressure acting on the diaphragm (actuation chamberpressure minus the force generated by the spring) should be greater thanthe combined pressure within the fuel tank plus the fuel head pressure.Otherwise, the pump outlet check valve 94 remains closed.

Second Exemplary Embodiment of a Mechanical Pump

FIGS. 8 through 10 illustrate a second exemplary embodiment of amechanical pump in the form of another pneumatic pump 232, which isdesigned to operate on negative, or vacuum, pulses from an engine intakemanifold, such as for a single or multiple cylinder four-stroke engine.The pneumatic pump 232 is adapted to generate relatively greaterpressure than the previously described pneumatic pump 32 to overcome atypical superatmospheric pressure within a fuel tank plus a typical fuelhead pressure. This embodiment is similar in many respects to theembodiment of FIGS. 5 through 7 and like numerals between theembodiments may generally designate like or corresponding elementsthroughout the several views of the drawing figures. Additionally, someof the common subject matter may not be repeated herein below.

FIGS. 8 and 9 illustrate the pneumatic pump 232, which is adapted to usenegative or vacuum pulses received from an engine intake manifold (notshown) to produce positive pressure pulses to actuate the diaphragm 280of the pump 232. The pump 232 includes a housing 274 and a cover 276attached to the housing with fasteners such as rivets 275 or the like,to define an interior 278. As shown in FIG. 9, a diaphragm 280 isdisposed within the interior 278 and is sealingly engaged between thecover 276 and the housing 274 to divide the interior 278 into a fuelreservoir 282 and an actuation chamber 284. A coiled compression spring286 is disposed within the fuel reservoir 282 to yieldably bias thediaphragm 280 against an annular projection 277 of the cover 276. Aspring plate 288 is received between the diaphragm 280 and the adjacentend of the spring 286. The other end of the spring 286 circumscribes acentral boss 290 that includes inlet and outlet check valves 292, 294disposed in fluid communication with the fuel reservoir 282 and inletsand outlets 296, 298 of the pump 232. The inlets and outlets 296, 298include respective inlet and outlet fittings 300, 302 inserted therein.At an opposite end of the pump 232, the cover 276 includes a pressureport 305 in communication with the actuation chamber 284 on one side anda vacuum pump 322 on the other.

Referring to FIGS. 9 and 10, the vacuum pump 322 is provided to convertnegative, or vacuum, pulses from an engine intake manifold (not shown)into positive pressure pulses to pressurize the actuation chamber 284.The vacuum pump 322 generally includes a valve plate 324 mounted againstthe cover 276 with a mounting gasket 326 between them, a diaphragm plate328 mounted against the valve plate 324 with a valve diaphragm 330between them, and a cover 332 that traps a vacuum diaphragm 334, spring336, and spring plate 338, and that is mounted against the diaphragmplate 328 and to the cover 276 with bolts 340 extending throughapertures in the diaphragms 330, 334, plates 324, 328, and gasket 326.

The vacuum pump 322 operates according to alternating vacuum pulses anda spring force to supply, for example, four to five psig of air pressuredepending on the magnitude of the incoming vacuum pulses. The vacuumpump 322 accepts vacuum pulses and incoming atmospheric air, and filtersthe incoming air and uses the vacuum pulses to move the air into theactuation chamber 284. The compression spring 336 normally biases thespring plate 338 and diaphragm 334 toward a bowl-shaped surface 342 inthe diaphragm plate 328. During engine operation, vacuum pulses arereceived through a fitting 344 in the cover 332 into a vacuum chamber346 defined between the diaphragm 334 and the cover 332. The vacuumpulses tend to evacuate the vacuum chamber 346 pulling the diaphragm 334toward the cover 332 against the bias force of the spring 336. Betweenvacuum pulses, the force of the spring 336 pushes the diaphragm 334 backtoward the diaphragm plate 328.

With each vacuum pulse, the valve plate 324 accepts incoming atmosphericair through a groove or channel therein that partially defines an inletpassage 348 between the valve plate 324 and the cover 276. An annularfilter 350 is disposed within a pocket 352 of the valve plate 324 tofilter the incoming air. The air flows through an aperture 354 in thevalve plate 324 and past an inlet valve flap 356 of the valve diaphragm330 that has a pinhole 358 therethrough. The air then flows through aninlet valve pocket 360 in the diaphragm plate 328 into a pressurechamber 362 defined between the vacuum diaphragm 334 and the bowl-shapedsurface of the diaphragm plate 328.

With each spring pulse, the air in the pressure chamber 362 issubstantially prevented from flowing out of the pump 322 by the inletvalve flap 356. Instead, the now pressurized air flows out of thepressure chamber 362 through an outlet passage 364 in the diaphragmplate 328 and past an outlet valve flap 366 of the valve diaphragm 330that has a pinhole 368 therethrough. The pressurized air flows throughan outlet valve pocket 370 and an outlet aperture 372 of the valve plate324 and out of the vacuum pump 322 through an outlet aperture 374 of themounting gasket 326.

The pneumatic pump 232 is powered by the positive pressure air pulsesreceived from its associated vacuum pump 322 to move the diaphragm 280from its retracted position shown in FIG. 9 to its advanced position(not shown). In its retracted position of FIG. 9, liquid fuel that waspreviously received from the carburetor 18 is temporarily stored in thefuel reservoir 282. When the engine is operating, positive pressurepulses of air from the vacuum pump 322 pass into the actuation chamber284. As air continues to enter the actuation chamber 284, air pressureincreases in the actuation chamber 284 and thereby displaces thediaphragm 280 in an advanced direction against the force of the spring286.

In its fully advanced position, the liquid fuel substantially has beenforced out of the fuel reservoir 282 through the outlet check valve 294and outlet 298 by displacement of the diaphragm 280 from its retractedposition against the annular projection 277 of the cover 276 to itsfully advanced position against the boss 290 of the housing 274. Thefuel is forced out of the pump 232 and into the rest of the fuel systemas described previously with respect to the first exemplary embodimentof the pump 32. Although some fluid from the actuation chamber 284 maypass through the pinholes 368, 358 of the valve flaps 366, 356 duringengine operation, the pinholes 368, 358 are preferably sized so that themagnitude and frequency of the air pressure pulses are sufficient tomaintain the diaphragm 280 in its forward state against the housing 274despite any pressure lost through the pinholes 368, 358.

The two previously described embodiments provide suitable reservoir andpneumatic pumps for removing fuel from a carburetor with many fuelsystem and engine configurations. But there may be other fuel system andengine applications that are not suited to such pneumatic pumps. Forexample, in some applications a fuel tank may be mounted very highrelative to a carburetor or the fuel tank may have relatively highinternal pressure compared to pressure pulse output of the associatedengine. In such applications, pneumatic style pumps may not be asdesirable as the alternative described below.

Third Exemplary Embodiment of a Mechanical Pump

FIG. 11 illustrates a third exemplary embodiment of a mechanical pump inthe form of a plunger actuated pump, or plunger pump 432, that isdesigned to operate based on manually imposed or spring imposed forcesto generate relatively greater pressure than the previously describedpneumatic pumps 32, 232 and thereby overcome internal fuel tank pressurecombined with fuel head pressure. This embodiment is similar in manyrespects to the embodiments of FIGS. 1 through 10 and like numeralsbetween the embodiments may generally designate like or correspondingelements throughout the several views of the drawing figures.Additionally, some of the common subject matter may not be repeatedherein below.

FIG. 11 illustrates the plunger pump 432 in an engine on position. Thepump 432 includes a housing 474 and a cover 476 attached to the housing474 with fasteners such as rivets 475 or the like, to define an interior478. As shown in FIG. 11, a diaphragm 480 is disposed within theinterior 478 between the housing 474 and the cover 476 to divide theinterior 478 into a fuel reservoir 482 and an actuation chamber 484. Acoiled compression spring 486 is disposed within the fuel reservoir 482and, via a spring plate 488 at one end, engages the diaphragm 480. At anopposite end of the spring 486, the spring 486 circumscribes a centralboss 490 that includes inlet and outlet check valves 492, 494 disposedin fluid communication with the fuel reservoir 482 and inlets andoutlets 496, 498 of the pump 432. The inlets and outlets 496, 498include respective inlet and outlet fittings 500, 502 inserted therein.

The plunger pump 432 includes a plunger apparatus 522 to convertpush-pull motion into displacement of the diaphragm 480 to dischargefuel out of the fuel reservoir 482. The plunger apparatus 522 generallyincludes a connector housing 524 engaged to the cover 476 for holding anactuator such as a push-pull cable assembly including a sheath 526 witha wire 528 slidably mounted therein. The wire 528 terminates in aball-shaped end 530 that is interengaged to a plunger 532 that includesa stem 534 that is slidably received in the connector housing 524. Anadvance spring 536 circumscribes the stem 534 of the plunger 532 and isseated within a spring seat 477 of the cover 476. The stem 534terminates in a spring plate 538 that receives the other end of thespring 536 and is adapted to be positioned against the diaphragm 480.

As shown, the plunger pump 432 is preferably actuated by movement of thepush-pull wire 528, which is preferably adapted for operating inaccordance with the safety bail 26, which is pivotably attached to thehandle 28 of the lawn mower 12 of FIG. 1. Those of ordinary skill in theart will recognize that the wire 528 is preferably attached to thesafety bail 26 on a side of the pivot axis of the safety bail 26opposite of where the push-pull cable for the valve 20 is attached.Alternatively, the wire 528 could be attached to the safety bail 26 viaa pivotable reversal link. In any case, when a user grips the safetybail 26 and moves it against the handle 28 in the engine runningposition 26′, the push pull wire 528 is adapted to relax or relieve theforce on the plunger 532 thereby allowing the spring 536 to move thediaphragm 480 from its retracted position (not shown) to its advancedposition as shown in FIG. 11. Thus, liquid fuel that was previouslyreceived from the carburetor 18 and that was temporarily stored in thefuel reservoir 482 is discharged out of the pump 432 by movement of thediaphragm 480. In the advanced position, the liquid fuel substantiallyhas been forced out of the fuel reservoir 482 through the outlet checkvalve 494 and outlet 498 by displacement of the diaphragm 480 from itsprevious retracted position to its new advanced position relativelyagainst the housing 474. The fuel is forced out of the pump 432 and intothe rest of the fuel system as described previously with respect to thefirst exemplary embodiment.

Upon engine shut down, such as when a user releases the safety bail 26from the handle 28, the push pull wire 528 may be adapted to retract theplunger 532 rearward to allow the diaphragm 480 to move from itsadvanced position as shown in FIG. 11 to its retracted position (notshown). Those of ordinary skill in the art will recognize that suitablelinkage may be interposed between the safety bail 26 and the plungerapparatus 522 to retract, rather than advance, the plunger 532 uponrelease of the safety bail 26. In any case, the plunger 532 rapidlyretracts and, thus, permits the spring 486 to displace the diaphragm 480rearwardly toward the cover 476, thereby increasing the volume of thefuel reservoir 482 and simultaneously decreasing the volume of theactuation chamber 484. As the volume of the fuel reservoir 482increases, liquid fuel is drawn out of the carburetor bowl 52 throughthe drain outlet 68, fitting 72, and fuel line 40 and into the fuelreservoir 482 through the inlet 496 and inlet check valve 492.

It is also contemplated that the plunger could be electromechanicallyactuated instead of manually actuated with the push pull cable. Forexample, the plunger could be adapted for use with a solenoid whereinthe stem of the plunger could be composed of magnetically responsivematerial for use as an armature of the solenoid. Those of ordinary skillin the art will recognize that push or pull solenoids could be adaptedfor use with the plunger stem, particularly latching solenoids to holdthe plunger in place in either or both of the advanced and retractedpositions. Alternatively, the plunger pump 432 could be manuallyactuated directly by a user's hand via a push-pull knob attached to theplunger 532.

Fourth Exemplary Embodiment of a Mechanical Pump

FIGS. 12 through 22 illustrate a fourth exemplary embodiment of amechanical pump in the form of a pneumatic pump 632, which is designedto operate on positive pressure pulses from an engine crankcase todischarge stored fuel. The pneumatic pump 632 does not include the valvepinholes of the previously described pneumatic pumps 32, 232 and, thus,generates relatively greater pressure than those pumps 32, 232.Moreover, the pneumatic pump 632 integrates the functionality of theshut off valve 20 of FIG. 2 so that the pneumatic pump 632simultaneously or sequentially stops flow of liquid fuel to thecarburetor 18 and draws liquid fuel therefrom substantially duringshutdown of the engine. Accordingly, the pneumatic pump 632 is basicallyan integrated pump and valve assembly. This embodiment is similar inmany respects to the embodiment of FIGS. 5 through 7 and like numeralsbetween the embodiments may generally designate like or correspondingelements throughout the several views of the drawing figures.Additionally, some of the common subject matter may not be repeatedherein below.

FIGS. 12 through 16 illustrate the pneumatic pump 632 in an engine offcondition. The pump 632 includes a housing 674 and a cover 676 attachedto the housing 674 with fasteners such as bolts 675 or the like, todefine an interior 678. As shown in FIGS. 14 and 15, a diaphragm 680 isdisposed within the interior 678 and is sealingly engaged between thecover 676 and the housing 674 to divide the interior 678 into a fuelreservoir 682 and an actuation chamber 684. A coiled compression spring686 is disposed within the fuel reservoir 682 to yieldably bias thediaphragm 680 against the annular projection 677 of the cover 676. Aspring plate 688 is received between the diaphragm and the adjacent endof the spring 686. At an opposite end of the spring 686, the spring 686circumscribes an annular projection 690 of the housing 674. Referring toFIGS. 15 and 16, inlet and outlet check valves 692, 694 are disposed influid communication with the fuel reservoir 682 via inlets and outlets696, 698 of the pump 632. The inlets and outlets 696, 698 communicatewith respective inlet and outlet fittings 700, 702 as will be describedbelow. At an opposite end of the pump 632, the cover 676 includes apressure port 705 in communication with the actuation chamber 684 on oneside and a pressure port 707 of the housing 674 on the other side.

Referring to FIGS. 12 through 16, a multi-functional shutoff valve 722is provided to control flow of fuel to and from the carburetor 18 aswell as control air pressure to and from an engine crankcase (notshown). Referring to FIG. 16, the shutoff valve 722 generally includes avalve plate 724 mounted against the housing 674 with a valve gasket 726between them, and a valve cover 728 that traps a rotary valve 730 and anexpanded metal spring 732, and is mounted against the valve plate 724with a cover gasket 734 between them and fastened to the housing 674with bolts 736 extending through apertures in the cover gasket 734,valve plate 724, and valve gasket 726. A lever 738 is fastened to therotary valve 730 through the cover 728 and is biased to an engine offposition, as shown, by a coiled torsional spring 740.

The engine on operation of the shutoff valve 722 and pump 632 isdescribed below in reference to FIGS. 14 through 22, wherein the lever738 may be rotated to the engine on position (not shown). The shutoffvalve 722 controls flow of liquid fuel from the fuel tank 16 to thecarburetor 18 and from the fuel reservoir 682 to either or both of thefuel tank 16 and carburetor 18. Liquid fuel flows into the pump 632 fromthe fuel tank 16 via a tank inlet fitting 742. The fuel flows through aportion of the valve plate 724 and out of an outlet fuel passage 743into the rotary valve 730 through a fuel channel 744 thereof. The fuelflows through and out of the fuel channel 744 and back into the valveplate 724 through an inlet fuel passage 745. The fuel flows through aportion of the valve plate 724 and out the outlet fitting 702 to thecarburetor 18. Additionally, liquid fuel flows out of the fuel reservoir682 through the fuel outlet 698 and the outlet check valve 694 disposedtherein, through an outlet aperture 746 of the valve gasket 726, intothe valve plate 724 via a fuel channel 747 in a pump side of the valveplate 724, and out of the valve plate through an outlet fuel passage748. The fuel then flows into the rotary valve 730 through the fuelchannel 744 and back into the valve plate 724 through either or both ofthe fuel passages 743 and 745. Accordingly, the fuel from the fuelreservoir 682 may ultimately flow to either or both of the fuel tank 16and carburetor 18 through the fuel fittings 742 and 702, respectively.

The shutoff valve 722 also controls flow of positive pressure pulses ofair from the engine crankcase to the actuation chamber 684 of the pump632. Pressure pulsed air flows into the valve plate 724 through apneumatic fitting 750. The air flows out of the valve plate 724 throughan outlet passage 751 and into the rotary valve 730. The pulsed airflows through a pneumatic channel 752 of the rotary valve 730 and backinto the valve plate 724 through an inlet passage 753. The pulsed airthen flows through an inlet check valve 706 disposed within the valveplate 724, through a pneumatic channel 754 in the pump side of the valveplate 724, through a pneumatic aperture 755 of the valve gasket 726 andinto the housing 674 of the pump 632 via the housing pressure port 707.As best shown in FIG. 15, the pulsed air flows through the internalhousing pressure port 707, through the internal cover pressure port 705,and into the actuation chamber 684. The pressurized air accumulates inthe actuation chamber 684 to move the diaphragm 680 away from the cover676 and toward the annular boss 690 of the housing 674 so as to displacethe volume of fuel stored in the fuel reservoir 682 out of the pump 632and to the tank 16 and/or carburetor 18.

The engine off operation of the shutoff valve 722 and pump 632 isdescribed below in reference to FIGS. 14 through 22, wherein the lever738 is shown rotated to the engine off position. The shutoff valve 722stops flow of liquid fuel from both the tank 16 and the fuel reservoir682 of the pump 632 to the carburetor 18. With the lever 738 in the offposition, fuel flow to the carburetor 18 is stopped, wherein thecarburetor inlet fuel passage 745 is stopped by an end portion 760 of apreferably elastomeric valve seal 761. Moreover, liquid fuel cannot flowinto the fuel reservoir 682 from the outlet fuel passage 743 through theoutlet fuel passage 748 because the outlet check valve 694, whichcommunicates with the outlet fuel passage 748 via fuel channel 747 onlypermits flow out of the fuel reservoir 682. Accordingly, liquid fuelfrom the fuel tank 16 may not flow through the valve 722.

The shutoff valve 722 also controls release of pressurized air back tothe engine crankcase from the actuation chamber 684 of the pump 632,thereby allowing the pump 632 to draw fuel out of the fuel bowl 52 ofthe carburetor 18. Referring again to FIG. 15, pressurized air flowsinto the shutoff valve 722 from the actuation chamber 684, through theinternal pressure ports 705, 707. The pressurized air flows through thevalve gasket aperture 755, into and through the channel 754 of the valveplate 724, around the check valve 706, through an outlet channel 762,and out the valve plate 724 via a pressure relief outlet passage 763.The pressurized air then flows through the pneumatic channel 752 in therotary valve 730, back into the valve plate 724 through a pneumaticpassage 751, and out of the shutoff valve 722 through the pneumaticfitting 750. Accordingly, the spring 686 is able to displace thediaphragm 680 in a direction relatively away from the housing 674 andtoward the cover 676 until the diaphragm 680 locates against the annularprojection 677 of the cover 676. Simultaneously, the movement of thediaphragm 680 pulls fuel through the carburetor inlet fitting 700 intothe valve plate 724, through a fuel inlet channel 765 in the pump sideof the valve plate 724, through a fuel inlet aperture 766 of the valvegasket 726, and through the inlet check valve 692 and inlet passage 696into the fuel reservoir 682. Thus, a relatively high pressure pump isprovided that integrates shutoff valve features and functionality toreduce the total number of individual components and connections withinthe fuel system.

Exemplary Embodiment of a Mechanical Pump and Carburetor Unit

FIGS. 23 through 26 illustrate an exemplary embodiment of a combinedcarburetor and mechanical pump 800. A carburetor portion 818 issubstantially similar to that described above with reference to FIGS. 1through 4. Likewise, a mechanical pump portion 832 is substantiallysimilar to that described above with reference to FIGS. 12 through 22.The basic differences between this embodiment and the related previouslydescribed embodiments, is that sub-assemblies are integrated into onelarger assembly to reduce the quantity of components in the fuel system,such as fluid lines and fittings. This embodiment is nearly identical inmany respects to the embodiments of FIGS. 1 through 4 and FIGS. 12through 22 and like numerals between the embodiments may generallydesignate like or corresponding elements throughout the several views ofthe drawing figures. Additionally, much of the common subject matter maynot be repeated herein below.

The carburetor 818 includes a carburetor body 844 that includes a chokelever 846 for operating a choke valve 847, a throttle lever 848 foroperating a throttle valve (not shown), and a preferred float bowl orfuel bowl 852 carried by the body 844. The fuel bowl 852 is preferablyangled according to the preferred design and construction as previouslydescribed herein.

As best shown in FIG. 25, the fuel bowl 852 includes an open end 854, awall 856 extending downward from the open end 854, and a closed end 858terminating the wall 856. On one side of the fuel bowl 852, the wall 856includes an extension 857 as will be discussed further below. The closedend 858 includes an inside bottom surface 860, 860′ that is sloped asdiscussed previously herein. The fuel chamber of the carburetor 818 isbasically defined between the inside bottom surface 860, 860′ of thefuel bowl 852 and the body 844.

The fuel bowl 852 is provided with a low-lying collection area 866 and afuel drain outlet 868 disposed substantially at the low-lying collectionarea 866 to enable substantially complete drainage of liquid fuel out ofthe fuel bowl 852. The low-lying collection area 866 is in fluidcommunication with the fuel chamber via a channel 870 provided in theclosed end 858 of the fuel bowl 852. The channel 870 slopes away fromthe inside bottom surface 860′ toward the low-lying collection area 866to enable liquid fuel to exit the fuel bowl 852 through a fitting 872.The fitting 872 includes an O-ring 873 and is carried by the extension857 and, on one end, is in communication with a bowl outlet passage 869provided in the fuel bowl 852. An opposite end of the fitting 872 isadapted for insertion into one end of a drain passage (not shown)provided in the carburetor body 844. The outlet passage 869 communicatesthe fitting 872 to the low-lying collection area 866 through the drainoutlet 868. To more fully ensure substantially complete drainage ofliquid fuel from the carburetor 818, it is further desirable to providemeans for removing the liquid fuel from the fuel bowl 852.

Such means may include the pump 832, which includes a housing 874 and acover 876 attached thereto with fasteners 875. A multi-functionalshutoff valve 922 is provided to control flow of fuel to and from thecarburetor 818 as well as to control air pressure pulses to and from anengine crankcase (not shown). The shutoff valve 922 generally includes avalve plate 924 mounted against the housing 874 via a valve gasket 926,and a valve cover 928 that is mounted against the valve plate 924 via acover gasket 934 and to the housing 874 with bolts 936. A lever 938extends through the cover 928 and is biased to an engine off position,as shown, by a coiled torsional spring 940.

The pump 832 is adapted to be mounted directly to the carburetor 818. Adrain fitting 900 and a carburetor fuel supply fitting 902 extendoutwardly from the housing 874 and are adapted for insertion intorespective drain and supply passages (not shown) in the carburetor body844. The drain fitting 900 is thus in fluid communication with the drain868 of the fuel bowl via the outlet passage 869, fitting 872, and bodydrain passage (not shown). Similarly, the fuel supply fitting 902 is influid communication with the carburetor fuel chamber via the body supplypassage (not shown) which is in fluid communication with the typicalchamber inlet passage (not shown) in the carburetor body 844. Thehousing 874 includes horizontal mounting extensions 880 and a verticalmounting extension 882. The horizontal mounting extensions 880 areadapted for mounting against a corresponding mounting extension 884 ofthe carburetor 818, and the vertical mounting extension is adapted formounting against a corresponding mounting extension (not shown) of thecarburetor 818. Bolts 886 preferably extend through the housingextensions 880, 882 and thread into the carburetor 818.

The pump 832, including the multi-functional shutoff valve 922substantially similar to the pump 732 and valve 722 which was describedwith regard to the previous embodiment and which is incorporated byreference herein.

Second Exemplary Embodiment of a Fuel System

FIGS. 27 through 30 illustrate in block diagram, another exemplaryembodiment of a fuel system that generally depicts many of the featuresof the previous embodiments and that includes some additional features.This embodiment is similar in many respects to the previously describedembodiments and like numerals between the embodiments generallydesignate like or corresponding elements throughout the several views ofthe drawing figures. Accordingly, some common subject matter may not berepeated in detail herein below.

The block diagrams of FIGS. 27 through 30 generally include anengine-powered apparatus or equipment 1012 having a combustion engine1014 for powering the equipment 1012 and a fuel system for storing anddistributing fuel to the engine 1014. The fuel system includes a fueltank 1016 for storing fuel, fuel lines or fluid paths for carrying fuel,a carburetor 1018 for mixing air with the fuel, and a combined fuel pumpand valve actuation device 1032 in fluid communication therebetween forcontrolling evaporative emissions of fuel. The fuel tank 1016 preferablyincludes a pressure relief valve 1043 that opens at internal fuel tankpressures in excess of four psig. The carburetor 1018 includes acarburetor body 1044, an air cleaner 1045 mounted to the body 1044 influid communication therewith as is well known in the art, and a fuelbowl 1052 mounted thereto in fluid communication with the body 1044.

The pump and valve actuation device 1032 preferably includes an interior1078 divided by diaphragm 1080 into a reservoir 1082 for fuel from acarburetor fuel bowl, and an actuation chamber 1084. The device 1032also preferably includes a valve actuation portion 1020 including threeactuated valves and three check valves. An actuated fuel tank vapor ventvalve 1176 is disposed in a fuel tank vapor fluid path 1178, 1178′extending between an upper portion of the fuel tank 1016 and the aircleaner 1045. An actuated fuel supply valve 1041 is disposed in a fuelsupply fluid path 1038, 1038′ extending between a lower portion of thefuel tank 1016 and the carburetor body 1044.

An actuated pressurized air valve 1161 is in a branched pressurized airfluid path 1153, 1153′, 1153″ between the actuation chamber 1084 and anengine crankcase 1015. The air valve 1161 is adapted to communicate theactuation chamber 1084 with one or the other of a pressure pulse branch1153′ or a pressure relief branch 1153″, but preferably not bothsimultaneously. In other words, the air valve 1161 can opencommunication between the actuation chamber 1084 and crankcase 1015through the relief passage 1153″, but simultaneously or synchronouslycloses communication between the actuation chamber 1084 and crankcase1015 through the pressure pulse passage 1153′.

The pump and valve actuation device 1032 also includes check valves. Apressure pulse check valve 1106 is in the pulse branch 1153′ of thebranched fluid path 1153, 1153′, 1153″ between the actuation chamber1084 and the engine crankcase 1015. A fuel reservoir inlet check valve1092 is in a carburetor drain fluid path 1091, and a fuel reservoiroutlet check valve 1094 is in a recycle fluid path 1093.

FIG. 27 illustrates the equipment 1012 in an engine running mode,wherein several fluid paths are preferably fully open. In this mode,liquid and vapor fuel flows from the fuel tank 1016 to the carburetor1018 when the engine 1014 is running. The pump and valve actuationdevice 1032 may be automatically actuated such as by a solenoid, or maybe manually actuated such as by a cable attached to a remote handle andlever of the equipment, so as to permit flow of liquid fuel and fuelvapors when the engine is running.

The pump and valve actuation device 1032 permits fuel vapor to flow fromthe fuel tank 1016, through the tank vapor inlet conduit 1178, throughthe fully open fuel tank vapor vent valve 1176, and through a tank vaporoutlet conduit 1178′, to the air cleaner 1045. Alternatively, it iscontemplated that the outlet conduit 1178′ may be communicated insteadto a carbon canister (not shown), the atmosphere, an engine intake port,any desired portion of the carburetor, or the like.

Also, the pump and valve actuation device 1032 permits liquid fuel toflow from the fuel tank 1016 through a liquid fuel inlet conduit 1038,through the fully open carburetor fuel inlet valve 1041, and through aliquid fuel outlet conduit 1038′, to the carburetor fuel chamber definedbetween the carburetor body 1044 and fuel bowl 1052, preferably by wayof the carburetor body 1044 and a float valve (not shown).

The check valves of the valve actuation device automatically permit orprevent flow of fuel or pressurized air therethrough. In the enginerunning situation, positive pulsed or pressurized air flows from thecrankcase 1015 through the check valve 1106, through the openpressurized air valve 1161 and into the actuation chamber 1084 to keepthe diaphragm 1080 in an advanced position. The air valve 1161 is opento permit pulses of air to flow to the actuation chamber 1084. Theinternal pressure of the chamber 1084 is preferably about 0.5 psig.

FIG. 28 illustrates the equipment 1012 in an engine shutdown mode,wherein the actuated valves are closing or have been closed. In thismode, neither liquid nor vapor fuel is permitted to flow from the fueltank 1016 to the carburetor 1018. The fuel tank vapor vent valve 1176 ofthe pump and valve actuation device 1032 closes so as to stop fuel vaporfrom flowing from the fuel tank 1016, through the tank vapor inletconduit 1178, and through the tank vapor outlet conduit 1178′, to theair cleaner 1045. Also, the carburetor fuel inlet valve 1041 closes tostop the flow of liquid fuel from the fuel tank 1016 through the liquidfuel inlet conduit 1038, and through the liquid fuel outlet conduit1038′, to the carburetor fuel chamber. As discussed with reference tothe previously disclosed embodiments, pressurized air from the actuationchamber 1084 is permitted to flow through the actuated pressurized airvalve 1161 and back into the engine crankcase 1015 to enable thediaphragm 1080 to be displaced and thereby draw fuel out of thecarburetor bowl 1052 into the reservoir 1082 through the inlet checkvalve 1092, while the outlet check valve 1094 prevents fuel from beingdrawn into the reservoir 1082 through the recycle fluid path 1093.During engine shutdown, the internal pressure of the chamber 1084decreases from about 0.5 psig to about 0.0 psi.

FIG. 29 illustrates the equipment 1012 in an engine off mode, whereinthe actuated valves are closed. As with the previous mode, in this mode,neither liquid nor vapor fuel is permitted to flow from the fuel tank1016 to the carburetor 1018. The fuel tank vapor vent valve 1176 of thepump and valve actuation device 1032 is fully closed so as to stop fuelvapor from flowing from the fuel tank 1016, through the tank vapor inletconduit 1178, and through the tank vapor outlet conduit 1178′, to theair cleaner 1045. Also, the carburetor fuel inlet valve 1041 is closedto stop flow of liquid fuel from the fuel tank 1016 through the liquidfuel inlet conduit 1038, and through the liquid fuel outlet conduit1038′, to the carburetor fuel chamber. Any air from the actuationchamber 1084 is still permitted to flow through the open pressurized airvalve 1161 and back into the engine crankcase 1015. By this point, allor substantially all fuel has been drained out of the carburetor bowl1052 through the passage 1091 and inlet check valve 1092 and is storedand sealed within the fuel reservoir 1082. Any build up of vaporpressure within the fuel reservoir 1082 is sealed by closing of theinlet check valve 1092 and is sealed from the carburetor inlet by theclosed carburetor inlet valve 1041. The fuel reservoir 1082 remains incommunication with the fuel tank 1016 through the check valve 1094. Theinternal pressure of the chamber 1084 is preferably only the headpressure due to the fuel in the fuel tank 1016. Shutoff of fuel supplyto the carburetor and withdrawal and storage of the bowl fuel reducesdiurnal losses by preventing fuel and/or fuel vapor from escaping fromthe fuel chamber.

FIG. 30 illustrates the equipment 1012 in an engine startup mode,wherein several fluid paths are open or are opening. Like the enginerunning mode, in this mode, liquid and vapor fuel flows from the fueltank 1016 to the carburetor 1018. The pump and valve actuation device1032 permits fuel vapor to flow from the fuel tank 1016, through thetank vapor inlet conduit 1178, through the open or opening fuel tankvapor vent valve 1176, and through the tank vapor outlet conduit 1178′,to the air cleaner 1045. Also, the pump and valve actuation device 1032permits liquid fuel to flow from the fuel tank 1016 through the liquidfuel inlet conduit 1038, through the open or opening carburetor fuelinlet valve 1041, and through a liquid fuel outlet conduit 1038′, to thecarburetor fuel chamber. Pulsed or pressurized air flows through thecheck valve 1106, through the open air valve 1161 and into the actuationchamber 1084 to displace the diaphragm 1080. The diaphragm 1080 isdisplaced to discharge fuel from the fuel reservoir 1082 through thecheck valve 1094, conduit 1093, and into conduit 1038 upstream of valve1041.

The present disclosure may also incorporate various components andfeatures of the fuel system described in U.S. patent application Ser.No. 10/955,781, filed Sep. 30, 2004, and entitled CONTROLLINGEVAPORATIVE EMISSIONS IN A FUEL SYSTEM, which is assigned to theassignee hereof and is hereby incorporated herein by reference.

Third Exemplary Embodiment of a Fuel System

FIG. 31 schematically illustrates another exemplary embodiment of a fuelsystem that generally depicts many of the features of the previousembodiments and that includes some additional features. This embodimentis similar in many respects to the previously described embodiments andlike numerals between the embodiments generally designate like orcorresponding elements throughout the several views of the drawingfigures. Accordingly, some common subject matter may not be repeated indetail herein below.

Referring now to FIG. 31, a gravity draining fuel system includes a fueltank 1216, a carburetor 1218 generally elevated with respect to the fueltank 1216, a pneumatically-actuated pump 1231 positioned generallybeneath the fuel tank 1216 in fluid communication between the carburetor1218 and the fuel tank 1216, and a four-way fitting 1233 positionedgenerally beneath the fuel tank 1216 in fluid communication between thefuel tank 1216 and carburetor 1218. In general, when the engine isoperating liquid fuel 1234 flows from the fuel tank 1216 through a fuelfilter 1236, fuel line 1238, pump 1231, and four-way valve 1233, intothe carburetor 1218. But when the engine is not operating, liquid fueldrains out of the carburetor 1218 and back to the fuel tank 1216 tosubstantially reduce evaporative emission of fuel from the carburetor1218.

The fuel tank 1216 is provided for containing liquid and vapor fuel andmay be sealed with any suitable cap or closure but is preferably sealedwith a non-vented cap 1242, which seals completely against a spout ofthe tank 1216 as shown. The fuel tank 1216 may be vented through a floatball check valve 1243, which communicates fuel vapor from the interiorof the fuel tank 1216 to a carbon canister (not shown) through a vaporline 1241. The valve 1243 may be a multiple function valve such as anatmospheric inlet and vapor outlet valve. For example, the valve 1243may be a roll over and anti-splash valve containing an anti-splash ballvalve, as shown, which does not allow liquid fuel to exit the fuel tank1216 during an extreme tilt angle or fuel splash. One preferred type ofthe valve 1243 is disclosed in U.S. patent application Ser. No.10/955,795, filed on Sep. 29, 2004, entitled EVAPORATIVE EMISSIONCONTROLS, which is assigned to the assignee hereof and is herebyincorporated herein by reference. Such a valve permits vapors to flowtherethrough and to a carbon canister when pressure in the fuel tank1216 exceeds a predetermined threshold. The fuel tank 1216 allows forcontinuous two way venting to assure that neither a substantial positivenor a substantial negative pressure is allowed to build up inside thefuel tank 1216, wherein the air and/or fuel vapor above the level offuel 1234 in the fuel tank 1216 is substantially at atmosphericpressure.

Referring to FIG. 32, the fuel pump 1231 includes inlet and outlet checkvalves 1277 and 1279 that are biased in closed positions againstpassages 1281 and 1283 respectively. The fuel pump 1231 is activated bypulses from the crankcase of a two or four stroke engine (not shown) orthe intake pulses from a four stroke engine (not shown) routed thrupulse line 1275. In any case, the fuel pump 1231 may be substantiallythe same as that disclosed in U.S. patent application Ser. No.10/955,133, filed on Sep. 30, 2004, and entitled EVAPORATIVE EMISSIONSCONTROLS IN A FUEL SYSTEM, which is assigned to the assignee hereof andis hereby incorporated herein by reference.

Referring to FIG. 34, the four way fitting 1233 provides a device toroute flow of fuel among the fuel tank 1216, carburetor 1218, and pump1231. The four way fitting 1233 includes a housing 1301 and severalfittings fitted thereto including an inlet fitting 1303, an outletfitting 1305, a bypass fitting 1307, and a return fitting 1309. Theinlet and outlet fittings 1303, 1305 define a through passage, thebypass fitting 1307 defines a bypass passage, and the return fitting1309 defines a return passage. A bypass check valve 1311 is disposedwithin the housing 1301 between the through passage and the bypasspassage to prevent fuel flow from the fuel tank 1216 further into thehousing 1301 and to permit fuel flow into the fuel tank 1216. A returncheck valve 1313 is disposed within the housing 1301 between the returnpassage and the through passage to prevent fuel flow from the housing1301 through the return passage and to permit fuel flow through thereturn passage further into the housing 1301. The check valves 1311,1313 are preferably identical and each includes a restriction orifice1315 to allow fuel flow therethrough and a valve disc 1317 to preventfuel flow therethrough. It is contemplated that the valves 1311, 1313,could also be constructed integrally with the fuel pump 1231, and thepump/valve integrated assembly could be placed inside the fuel tank1216.

Referring to FIG. 33, aside from the novel features described herein,the carburetor 1218 may otherwise be constructed consistent with a lowevaporative emission float-bowl carburetor, as discussed previouslyherein. In general, however, the carburetor 1218 includes a carburetorbody 1244 and a fuel inlet fitting 1250 that communicates with a bowlvent check valve 1251 disposed in a bowl vent passage 1253 in thecarburetor body 1244 and with an inlet needle valve 1365 disposed withina fuel inlet passage 1361. The carburetor 1218 also includes a preferredfloat bowl or fuel bowl 1252 carried by the body 1244, and a combinationfloat arm and float 1264.

The fuel bowl 1252 may be of preferred design and construction includingan open end 1254, a wall 1256 extending downward from the open end 1254,and a closed end 1258 terminating the wall 1256, wherein the closed end1258 includes an inside bottom surface 1260, 1260′ that is sloped towarda low-lying collection area 1266 and a fuel drain outlet 1268 disposedsubstantially at the low-lying collection area 1266 through the bottomof the fuel bowl 1252 as opposed to through the side as with otherembodiments. As with previous embodiments, the fuel drain outlet 1268 ispositioned in such proximity to the low-lying collection area 1266 so asto enable substantially complete drainage of liquid fuel out of the fuelbowl 1252 through the fuel drain outlet 1268. A bowl outlet fitting 1272is mounted to the bottom of the fuel bowl 1252 in communication with thedrain outlet 1268. The fuel chamber of the carburetor 1218 is basicallydefined between the inside bottom surface 1260, 1260′ of the fuel bowl1252 and the body 1244.

Referring to FIGS. 31 through 34 generally, during engine operation,fuel exits the fuel tank 1216 thru the standard fuel pick-up and filter1236 and fuel line 1238 to the fuel pump 1231. The pump 1231 pumps fuelto the carburetor 1218 thru fuel line 1238′, four way fitting 1233, andfuel line 1238″. In each of the check valves 1311, 1313 of the four wayfitting, the restriction 1315 is preferably kept to a minimum (e.g.˜0.020″ or smaller) to facilitate starting of the engine, especiallyhand cranking of the engine. Because the fuel lines 1238, 1238′, 1238″and the carburetor bowl 1252 are ordinarily empty upon startup, fuel ispumped to fill these components during the starting process.Accordingly, the restrictions 1315 are preferably small enough toprevent complete drain back of the fuel between each pull of the enginestarting rope (not shown). A starting fuel primer (not shown), which iscommon on lawn and garden equipment preferably would aid in starting theengine in this embodiment. While the check valves 1311, 1315 arepreferably identical, the diameter of the restrictions 1315 may havedifferent values depending on the check valve 1311 or 1313.

Fuel pumped from the pneumatic pump 1231 can also flow through thebypass check valve 1311 of the four way fitting 1233 back to the fueltank 1216 through the bypass fitting. Nonetheless, the pump 1231 ispreferably sized such that the output capacity of the pump 1231 issufficient to supply adequate fuel flow and pressure up to thecarburetor 1218, despite the flow of bypass fuel thru the check valve1311. The fuel pressure delivered from the fuel pump 1231 acts againstthe disk 1317 of the return check valve 1313 and is sufficient to keepthe valve 1313 closed and block fuel flowing from fuel line 1240 throughthe four way fitting 1233. Even if there is some small flow out of thefuel bowl 1252 thru the outlet fitting 1272, the fuel pump 1231 ispreferably sized to deliver adequate fuel flow and pressure to thecarburetor inlet. The restriction orifice 1315 in the check valve 1313is sized to prevent rapid flow of fuel from the fuel bowl 1252 even ifthe fuel pressure should momentarily drop, such as between startingpulls. The bowl vent check valve 1251 in the carburetor body 1244 doesnot allow fuel to bypass the inlet needle 1365 as it is positioned toallow flow only in the opposite direction, such as fuel vapor flow.Accordingly, the float bowl 1252 of the carburetor 1218 is filled duringall phases of engine operation with the carburetor inlet needle valve1365 regulating the flow of incoming fuel.

Still generally referring to FIGS. 31 through 34, when the engine isturned off, the pulses from the crankcase (or the engine revolutionsdriving a mechanical pump or the electric current driving an electricpump) cease and fuel flow thru the pump 1231 stops. Also, the tankpressure above the fuel level 1234 is atmospheric, and back pressure onthe disc 1317 of the return check valve 1313 drops to a value equal tothe fuel head between the top of the fuel level 1234 in the fuel tank1216 and the valve 1313. Also, one or more of the inlet or outlet checkvalves 1277 or 1279 of the fuel pump 1231 or the check valves 1311 or1313 of the four way fitting 1233 is in fluid communication between thefuel tank 1216 and the carburetor 1218 and is adapted to prevent flow offuel into the carburetor 1218 at least when the internal combustionengine is not operating.

Moreover, fuel drains from the carburetor bowl 1252 and flows thru thereturn fuel line 1240, through the return check valve 1313, through thebypass valve 1311, and through the bypass passage back to the fuel tank1216. The fuel in fuel line 1238″ drains back to the fuel tank 1216 asair from the carburetor bowl vent passage 1253 flows thru the bowl ventcheck valve 1251, thereby preventing a vacuum build up on the tip of theinlet needle valve 1365 that is exposed to the fuel inlet passage 1361.The vent check valve 1251 is especially preferable in cases of high fuellift between the fuel tank 1216 and the carburetor 1218 on the order offive feet or more. Normally, however, fuel draining from the carburetorbowl 1252 thru the outlet fitting 1272 will lower the fuel level in thefuel bowl 1252, thereby lowering the float 1264 and, thus, opening theinlet needle valve 1365 and allowing air flow into fuel line 1238″ toallow fuel to drain back to the fuel tank 1216.

The fuel does not all drain back into the fuel tank 1216 through thebypass valve 1311. The fuel in lines 1238″ and 1240 will drain to alevel equal to the height of the fuel 1234 in the fuel tank 1216. Bycleverly constructing the fuel pump 1231 and valves 1311, 1313, and bykeeping the inside diameter of the fuel lines 1238, 1238′, 1238″, 1240to a minimum acceptable size, the fuel remaining in the fuel lines 1238,1238′, 1238″, 1240 is kept to a minimum. If, by chance, some fuel in thefuel lines 1238, 1238′, 1238″, 1240 heats up and escapes to theatmosphere during diurnal storage, that amount of fuel is prevented frombeing replenished by additional fuel in the tank 1216 by the fuel pumpvalves 1277, 1279. Accordingly, this fuel system automatically drainsthe carburetor bowl 1252 at engine shut down by gravity draining,thereby limiting the evaporative emissions loss to the atmosphere.

Fourth Exemplary Embodiment of a Fuel System

FIG. 35 illustrates in a block diagram, and FIG. 36 illustrates in apictorial schematic, another exemplary embodiment of a fuel system thatgenerally depicts many of the features of the previous embodiments andthat includes some additional features. This embodiment is similar inmany respects to the previously described embodiments and like numeralsbetween the embodiments generally designate like or correspondingelements throughout the several views of the drawing figures.Accordingly, some common subject matter may not be repeated in detailherein below.

The block diagram of FIG. 35 generally includes an engine-poweredapparatus or equipment 1412 having a combustion engine (not shown) forpowering the equipment 1412 and an electrically-actuated orsolenoid-actuated fuel system for storing and distributing fuel to theengine. The fuel system includes a fuel tank 1416 for storing fuel, fuellines or fluid paths for carrying fuel, a carburetor 1418 for mixing airwith the fuel, a valve actuation device 1420 in fluid communicationtherebetween and actuated by a solenoid 1421 for controlling evaporativeemissions of fuel, and a mechanical pump 1432 in fluid communicationtherebetween and actuated by a second solenoid 1435 for activelydraining the carburetor 1418 of fuel.

The components of the system include various sub-components. The fueltank 1416 preferably is communicated to a carbon canister 1417 via avent line 1578. The carburetor 1418 includes a carburetor body 1444, anair cleaner 1445 mounted to the body 1444 in fluid communicationtherewith as is well known in the art, and a fuel bowl 1452 mountedthereto in fluid communication with the body 1444. The pump 1432preferably includes an interior 1478 divided by diaphragm 1480 into areservoir 1482 for fuel from a carburetor fuel bowl, and an actuationchamber 1484. The pump 1432 also includes a fuel reservoir inlet checkvalve 1492 in a carburetor drain fluid path 1491, and a fuel reservoiroutlet check valve 1494 in the recycle fluid path 1493. The valveactuation device 1420 includes an actuated fuel supply valve 1441disposed in a fuel supply fluid path 1438, 1438′ extending between alower portion of the fuel tank 1416 and the carburetor body 1444.

The fuel system uses the two solenoids 1421 and 1435 which are wired tobe electrically switched on and off simultaneously. The solenoids 1421,1435 may be electrically connected to a power supply such as a batteryof the equipment 1412, as is known to those of ordinary skill in theart. The first solenoid 1421 operates the fuel supply valve 1441 betweenthe fuel tank 1016 and the fuel inlet to the carburetor body 1444. Thesecond solenoid 1435 operates the diaphragm 1480 of the fuel bowl drainpump 1432.

When engine controls (not shown) are in the engine “ON” position,electric current flows to both solenoids 1421, 1435 applying a force tosolenoid armatures 1423, 1437 in a direction tending to center thearmatures 1423, 1437 in solenoid wire windings 1425, 1439. The armature1423 of the first solenoid 1421 is attached by means of a mechanicallink 1537 to a lever 1538 that controls the fuel supply valve 1420,which lever 1538 is biased in a closed position by means of a torsionalspring 1540. When the engine is switched “ON”, the armature 1423 ispulled into the center of the solenoid winding 1425, thereby overcomingthe torsional bias of the spring 1540 and, thus, opening the valve 1420.Preferably, the armature 1423 reaches full travel very quickly, thusopening the valve very quickly (i.e. ˜one second or less). The armature1437 of the second solenoid 1435 is attached mechanically to a plunger1532 on an actuation side of the diaphragm 1480 of the pump 1432. Thediaphragm 1480 is normally biased in the interior 1478 by an internalcompression spring 1486. The armature 1437 applies a force that movesthe diaphragm 1480 to the position shown to empty the reservoir 1482 andthereby displace fuel through the outlet check valve 1494 back to ortoward the fuel tank 1416. The armature 1437 of the second solenoid 1435moves slower to its centered position than does the armature 1423 of thefirst solenoid 1421, because displacing the reservoir fuel through theoutlet check valve 1494 may take several seconds to perhaps a minute ormore.

When the engine controls (not shown) are in the engine “OFF” position,there is no electrical current flowing to either of the solenoids 1421,1435. In this mode, there is no force being applied to either armature1423, 1437 and the armatures 1423, 1437 are easily moved by therespective biasing springs 1540, 1486 of the fuel supply valve 1420 andof the pump 1432. The supply valve 1420 is switched to the off positionquickly and the reservoir 1482 of the pump 1432 is filled with fuel fromthe carburetor bowl 1452 through the inlet check valve 1492 relativelyslowly.

It is contemplated, however, that if both armatures 1423, 1437 were ableto move rapidly to their full centered positions, then only one solenoidwould be required with mechanical linkage from the solenoid to both thevalve 1420 and pump 1432. Even with the valve 1420 and pump 1432requiring vastly different actuation times, one solenoid could be usedif the armature thereof was allowed to move quickly and mechanicallinkage to the slower moving pump 1432 stored the energy to complete theoperation. For instance, the mechanical linkage could be a lost-motionlinkage and/or could include a compressed spring which would slowlyuncompress to complete the diaphragm movement function.

CONCLUSION

One or more of the various embodiments described herein may provide oneor more of the advantages described herein below. During startup and/orrunning of an internal combustion engine, at least one or more of thefollowing actions may be permitted: venting of fuel vapor from a fueltank, and supplying fuel to the carburetor from at least one of the fueltank and a fuel bowl drain reservoir. Conversely, during shut downand/or when the internal combustion engine is not operating, acarburetor fuel bowl is drained of substantially all of its liquid fuelto at least one of the fuel tank and the fuel bowl drain reservoir, andat least one or more of the following actions are prevented: venting offuel vapor from the fuel tank, supplying fuel from the carburetor to atleast one of the fuel tank and a fuel bowl drain reservoir. Accordingly,evaporative emissions from a carburetor of a fuel system are able to bereduced. Moreover, the various valves are automatically closed at thevalve or valve device itself to make the evaporative emission controlsfail safe. Finally, the multi-action valve arrangement of theabove-described embodiments of the present invention easily integratesmultiple valve actions into one mechanism.

It is to be understood that the foregoing description is not adescription of the invention, but is a description of one or morepresently preferred embodiments of the invention. Accordingly, theinvention is not limited to the particular exemplary embodiment(s)disclosed herein, but rather is defined solely by the claims below. Inother words, the statements contained in the foregoing descriptionrelate to particular exemplary embodiments and are not to be construedas limitations on the scope of the invention as claimed below or on thedefinition of terms used in the claims, except where a term or phrase isexpressly defined above or where the statement specifically refers to“the invention.” Various other embodiments and various changes andmodifications to the disclosed embodiment(s) will become apparent tothose skilled in the art. All such other embodiments, changes, andmodifications are intended to come within the scope of the appendedclaims.

As used in this specification and claims, the terms “for example,” “forinstance,” and “such as,” and the verbs “comprising,” “having,”“including,” and their other verb forms, when used in conjunction with alisting of one or more components or other items, are each to beconstrued as open-ended, meaning that the listing is not to beconsidered as excluding other, additional components, elements, oritems. Moreover, directional words such as top, bottom, upper, lower,radial, circumferential, axial, lateral, longitudinal, vertical,horizontal, and the like are employed by way of description and notlimitation. Other terms are to be construed using their broadestreasonable meaning unless they are used in a context that requires adifferent interpretation. When introducing elements of the presentinvention or the embodiment(s) thereof, the articles “a,” “an,” “the,”and “said” are intended to mean that there are one or more of theelements.

While the forms of the invention herein disclosed constitute presentlypreferred embodiments, many others are possible. The method ispreferably carried out using various elements of the system, and, inturn, the system preferably includes various elements of the apparatus,although the present invention contemplates a myriad of alternatives. Inother words, any given manifestation or embodiment of the presentinvention is not to be read as limited to the limitations of otherembodiments of the present invention. More specifically, any givenembodiment disclosed herein, and any features associated therewith, areinterchangeable and incorporated by reference into any other givenembodiment disclosed herein. Accordingly, the present inventioncontemplates that each feature of each embodiment disclosed herein iscombinable with other features of the other embodiments disclosedherein. Also, it is contemplated that the present invention can beadapted for use with carburetors that may include an integral fuel bowlas opposed to a fuel bowl that is separately mounted to the carburetorbody. It is not intended herein to mention all the possible equivalentforms or ramifications of the invention. It is understood that termsused herein are merely descriptive, rather than limiting, and thatvarious changes may be made without departing from the spirit and scopeof the invention as defined by the following claims.

1. A method of controlling evaporative emissions of volatile fuel from afuel system including a fuel tank and a carburetor for use with aninternal combustion engine, the method comprising the steps of:containing fuel within the fuel tank and within the carburetor;permitting flow of fuel into the carburetor, at least when the internalcombustion engine is operating; preventing flow of fuel into thecarburetor, at least when the internal combustion engine is notoperating; and permitting flow of fuel out of the carburetor and into areceptacle, substantially during shutdown of the internal combustionengine.
 2. The method of claim 1 further comprising withdrawing fuel outof the carburetor and into the receptacle, substantially during shutdownof the internal combustion engine.
 3. The method of claim 2 wherein thewithdrawing step includes using a pneumatically-actuated diaphragm pump.4. The method of claim 2 wherein the withdrawing step includes using anelectrically-actuated pump.
 5. The method of claim 1 wherein thecarburetor is elevated with respect to the fuel tank such that the stepof permitting flow of fuel out is enabled by gravity flow of fuel. 6.The method of claim 5 wherein the receptacle is the fuel tank.
 7. Themethod of claim 1 wherein the receptacle is separate from the fuel tank.8. The method of claim 7 further comprising permitting flow of fuel fromthe receptacle to at least one of the fuel tank, the carburetor, or afluid path therebetween, substantially during startup of the engine. 9.The method of claim 8 further comprising pumping fuel from thereceptacle with a pneumatically-actuated diaphragm pump.
 10. The methodof claim 1 further comprising: permitting flow of fuel vapor into thecarburetor, at least when the internal combustion engine is operating;and preventing flow of fuel vapor into the carburetor, at least when theinternal combustion engine is not operating.
 11. A fuel system forsupplying fuel to an internal combustion engine, the fuel systemcomprising: a fuel tank for containing fuel therein; a carburetor influid communication with the fuel tank by at least one fluid path; avalve in fluid communication between the fuel tank and the carburetorand being adapted to prevent flow of fuel into the carburetor, at leastwhen the internal combustion engine is not operating; and a pump influid communication with the carburetor and being adapted to pump fuelout of the carburetor, substantially during shutdown of the internalcombustion engine.
 12. The fuel system of claim 11 wherein the pumpincludes a fuel reservoir and is adapted to pump fuel out of thecarburetor and into the fuel reservoir, substantially during shutdown ofthe internal combustion engine and is further adapted to pump fuel outof the reservoir to at least one of the fuel tank, the carburetor, orthe at least one fluid path therebetween, substantially during startupof the internal combustion engine.
 13. The fuel system of claim 11wherein the pump is a pneumatically-actuated diaphragm pump.
 14. Thefuel system of claim 11 wherein the pump is an electrically-actuatedpump.
 15. The fuel system of claim 11 wherein the valve is furtheradapted to permit flow of fuel vapor from the fuel tank to thecarburetor at least when the internal combustion engine is operating andprevent flow of fuel vapor from the fuel tank to the carburetor at leastwhen the internal combustion engine is not operating.
 16. The fuelsystem of claim 11 wherein the carburetor includes: a body for mixingair with fuel for delivery to the engine; a float carried by the bodyand being movable about a pivot axis; and a fuel bowl carried by thebody, wherein a fuel chamber is defined therebetween for containingfuel, the fuel bowl includes a closed end having an inside bottomsurface sloped generally downwardly away from the pivot axis and furtherhaving a low-lying collection area and a fuel drain outlet disposedsubstantially at the low-lying collection area to enable substantiallycomplete drainage of fuel out of the fuel bowl.
 17. The fuel system ofclaim 11 wherein the carburetor includes a fuel bowl comprising: an openend; a wall portion extending from the open end; and a closed endterminating the wall portion, the closed end including a low-lyingcollection area and a fuel drain outlet disposed substantially at thelow-lying collection area.
 18. The fuel system of claim 11 wherein thepump and the valve are integrated into a pump and valve assembly. 19.The fuel system of claim 18 wherein the carburetor and the pump andvalve assembly are adapted for assembly as a single unit.
 20. The fuelsystem of claim 11 wherein the pump comprises: an interior; a diaphragmdisposed within the interior to divide the interior into a fuelreservoir on a reservoir side of the diaphragm and an oppositelydisposed actuation chamber on an oppositely disposed actuation side ofthe diaphragm; a biasing member to yieldably bias the diaphragm; a fuelinlet in communication with the fuel reservoir; an inlet check valve incommunication with the fuel inlet; a fuel outlet in communication withthe fuel reservoir; and an outlet check valve in communication with thefuel outlet.
 21. A fuel system for supplying fuel to an internalcombustion engine, the fuel system comprising: a fuel tank forcontaining fuel therein; a carburetor elevated with respect to the fueltank and in fluid communication therebetween by at least one fluid path;at least one valve in fluid communication between the fuel tank and thecarburetor, the at least one valve being adapted to prevent flow of fuelinto the carburetor and permit flow of fuel away from the carburetor, atleast when the internal combustion engine is not operating; and a pumpin fluid communication with the carburetor, the pump being adapted topump fuel to the carburetor substantially during startup and operationof the internal combustion engine.
 22. A carburetor of a fuel systemthat includes a fuel tank for containing fuel and that is adapted foruse with an internal combustion engine, the carburetor comprising: abody for mixing air with fuel for delivery to the engine; a floatcarried by the body and being movable about a pivot axis; and a fuelbowl carried by the body, wherein a fuel chamber is defined therebetweenfor containing fuel, the fuel bowl includes a closed end having aninside bottom surface sloped generally downwardly away from the pivotaxis and further having a low-lying collection area and a fuel drainoutlet disposed substantially at the low-lying collection area to enablesubstantially complete drainage of fuel out of the fuel bowl.
 23. Thecarburetor of claim 22 wherein the fuel bowl includes a drain channelprovided in the inside bottom surface and in communication with thelow-lying collection area.
 24. A fuel bowl for containing fuel for acarburetor, comprising: an open end; a wall portion extending from theopen end; and a closed end terminating the wall portion, the closed endincluding a low-lying collection area and a fuel drain outlet disposedsubstantially at the low-lying collection area to enable substantiallycomplete drainage of fuel out of the fuel bowl.
 25. The fuel bowl ofclaim 24 wherein the closed end further includes an inside bottomsurface that is sloped substantially toward the low-lying collectionarea.
 26. The fuel bowl of claim 25 wherein the closed end furtherincludes a drain channel provided in the inside bottom surface and incommunication with the low-lying collection area.
 27. A fuel pump of afuel system including a fuel tank and a carburetor adapted for use withan internal combustion engine, comprising: a diaphragm disposed withinan interior of the fuel pump to divide the interior into a fuelreservoir on a reservoir side of the diaphragm and an oppositelydisposed actuation chamber on an actuation side of the diaphragm; abiasing member to yieldably bias the diaphragm; a fuel inlet incommunication with the fuel reservoir; an inlet check valve incommunication with the fuel inlet; a fuel outlet in communication withthe fuel reservoir; and an outlet check valve in communication with thefuel outlet.
 28. The fuel pump of claim 27 further comprising: ahousing; and a cover carried by the housing to define the interiortherebetween, the diaphragm being sealingly engaged between the housingand the cover.
 29. The fuel pump of claim 28 further comprising a vacuumpump mounted to the cover and being adapted to convert vacuum pulsesreceived from an external source into pressure pulses to pressurize theactuation chamber.
 30. The fuel pump of claim 29 wherein the vacuum pumpcomprises: a valve plate positioned against the cover; a diaphragm platepositioned against the valve plate; a valve diaphragm positioned betweenthe valve plate and diaphragm plate and including an inlet valve and anoutlet valve; a cover positioned against the diaphragm plate; adiaphragm positioned between the cover and the diaphragm plate; and abiasing means positioned between the diaphragm and the cover.
 31. Thefuel pump of claim 28 further comprising a plunger apparatus carried bythe cover and being adapted to convert push-pull motion intodisplacement of the diaphragm.
 32. The fuel pump of claim 31 wherein theplunger apparatus comprises: a plunger including a plate portionpositioned against the diaphragm and a stem portion extending from theplate portion through an aperture in the cover; and a biasing memberpositioned between the plate portion of the plunger and the cover. 33.The fuel pump of claim 28 further comprising a valve actuation devicemounted to the housing and being in fluid communication between the fueltank and the fuel chamber of the carburetor, wherein the valve actuationdevice permits flow of fuel from the fuel tank to the carburetor whenthe internal combustion engine is operating, and further wherein thevalve actuation device prevents flow of fuel from the fuel tank to thecarburetor when the internal combustion engine is not operating.
 34. Thefuel pump of claim 33 wherein the valve actuation device comprises: avalve plate positioned against the housing; a cover positioned againstthe valve plate; and a rotatable valve positioned between the cover andthe valve plate, the rotatable valve being rotatably biased to a valveclosed position so as to automatically stop flow of fuel through atleast one passage.
 35. The fuel pump of claim 28 wherein the coverincludes a pressure port therein adapted to communicate pressurized airinto and out of the actuation chamber.
 36. A method of reducingevaporative emissions from a carburetor, which includes a fuel bowl, afuel inlet passage in communication with the fuel bowl, an inlet valveto valve the inlet fuel passage, a float pivotable about a float pivotaxis, and a fuel nozzle jet to communicate fuel within the fuel bowl toa fuel nozzle, the method comprising: minimizing at least one of thesize of the inlet fuel passage or the lateral distance between floatpivot axis and at least one of the vertical axis of the inlet fuelpassage or the inlet valve; and maximizing at least one of the fuelcontact surface area of the float or the lateral distance between thefloat pivot axis and a vertical axis of a fuel buoyancy force associatedwith the float; wherein the volume of fuel within the fuel bowl issubstantially minimized.
 37. The method of claim 36 wherein the step ofminimizing includes minimizing both the size of the inlet fuel passageand the lateral distance between float pivot axis and the axis of theinlet fuel passage.
 38. The method of claim 37 wherein the step ofmaximizing includes maximizing both the fuel contact surface area of thefloat and the lateral distance between the float pivot axis and thevertical axis of the fuel buoyancy force associated with the float. 39.The method of claim 36 wherein the step of maximizing includesmaximizing the fuel contact surface area of the float and the lateraldistance between the float pivot axis and the fuel buoyancy forceassociated with the float.
 40. The method of claim 39 wherein the stepof minimizing includes minimizing both the size of the inlet fuelpassage and the lateral distance between float pivot axis and the axisof the inlet fuel passage.
 41. The method of claim 36 furthercomprising: angling an inside bottom surface of the fuel bowl.
 42. Themethod of claim 41 further comprising: angling the inside bottom surfaceof the fuel bowl laterally and downwardly away from the float pivotaxis.
 43. The method of claim 42 further comprising: angling the insidebottom surface of the fuel bowl toward a low-lying collection area ofthe fuel bowl.